Kidney Anatomy and Function PDF

Kidneys Normal anatomy **Paired Kidneys** Retroperitoneum Lie against deep muscles of back lateral to vertebra Produce urine Right more inferior than left in location **Paired Ureters** convey urine from kidneys to bladder **Urinary Bladder** Stores urine **Urethra** Drains urine from bl...

Kidneys Normal anatomy **Paired Kidneys** Retroperitoneum Lie against deep muscles of back lateral to vertebra Produce urine Right more inferior than left in location **Paired Ureters** convey urine from kidneys to bladder **Urinary Bladder** Stores urine **Urethra** Drains urine from bladder to outside body Diagram of the urinary system Description automatically generated Embryology - 3 Pairs of Kidneys differentiate in successive intervals of development - **[1- Pronephros-]** (fore kidney) non-functional and disappear around 4^th^ week - **[2- Mesonephros-]** (mid kidney) partial function in 1^st^ trimester (5^th^ week) - Give rise to mesonephric tubule and ducts - Male- Wolffian ducts and develop the male genetalia - Female- Mullerian ducts (paramesonephric ducts) eventually into the uterus and vagina (Gartner duct) - **[3- Metanephros]** -- the permanent kidney- uretic buds and the mesenchyme (blastema) interact to induce the complete functioning formation of kidney  **[Size and antomy ]** About the size of a clenched fist Length -- 9-12 cm Width- 5- 7 cm Height (Thick) -- 2- 3 cm \* Should be within 2 cm of each other in length Layers **[Inner- Fibrous Renal Capsule]** covers surface and gives glistening appearance **[Middle- Perirenal Fat-adipose capsule]** cushions kidney and holds kidney in place **[Outer --Renal Fascia/Gerota's Fascia]** dense, fibrous connective tissue surround kidney fat, and adrenal gland **[Pararenal Fat most outer later-]** anterior and posterior At the **[HILUM]** of kidney, the [**VEIN**] exits anteriorly **[ARTERY]** enters between vein & ureter **[URETER]** exits posteriorly C:\\Kawamura\\processed\\figure\_10.1.jpg Relational anatomy **[Right Kidney ]** Adrenal gland is superor- medial Liver is superor- lateral Right colic flexure is inferior 2^nd^ portion of duodenum is medial **[LEFT KIDNEY]** Adrenal gland and spleen are superior Pancreatic tail is anterior to upper pole Left colic flexure is inferior  Kidney anatomy **[Rena Cortex-]** outer parenchyma from base of pyramids to capsule (normal is \> 1cm) **[Renal Medulla-]** inner portion of kidney from base of pyramid to center of kidney **[Renal Sinus-]** inner hyperechoic portion of kidney containing fat, calyces, renal pelvis, connective tissue, renal vessels, & lymphatics **[Medullary pyramids-]** anechoic, equally spaced triangles of collecting tubules between cortex and renal sinus. See often in neonates and pediatric kidneys **[Renal pelvis-]** funnel shaped transition from major calyces to ureter **[Renal hilum-]** medial opening for entry/ exit of artery, vein, ureter **[Major Calyces-]** 3 extensions for the renal pevis **[Minor Calyces-]** extensions of major calyces that collect urine from medullary pyramid. \# of minor calyces = \# of medullary pyramids **[Renal Papilla-]** apex of medullary pyramids **[Gerota's Fascia-]** fibrous sheath enclosed kidney and adrenal gland. Also referred to as the perirenal space **[Nephron-]** functional unit of kidney that consists of renal corpuscle, proximal convoluted tubule, descending and ascending limbs of Henle's loop, distal convoluted tubule, and collecting tubules. **[Renal corpuscle (Malpighian body)-]** consists of glomerulus and glomerular capsule (Bowman's capsule) Renal vasculture - Kidneys are supplied with arterial blood via **[main renal artery]** which branches off aorta - At hilum, main renal artery divides into **[5 segmental arteries]** - Between the medullary pyramids, the segmental arteries divide into **[interlobar arteries,]** which travel perpendicular to renal capsule. - At the base of medullary pyramids, **[arcuate arteries]** branch from interlobar arteries (**parallel to renal capsule**). Often the arcuate arteries are difficult to obtain an ideal spectral waveform because they travel perpendicular to the Doppler sound beam - **[Interlobular arteries]** are the smallest renal arteries that branch off the arcuate arteries running perpendicular to renal capsule **Blood flow** **Main renal**- **Segmental**- **Interlobar**- **Arcuate**- **Interlobular** A ultrasound image of a liver Description automatically generated Sonographic appearance **[ECHOGENICITY]** **[Renal Cortex-]** Isoechoic or Hypoechoic relative to liver & Spleen **[Medullary Pyramids-]** Anechoic Ren**[al Sinus-]** Hyperechoic Echo Amplitude of renal structures in ascending order Renal Medulla \< Renal Cortex \< Liver \< Spleen \< Pancreas \< Diaphragm \< Renal Sinus = Renal Capsule A ultrasound image of a liver Description automatically generated  A. Longitudinal section through right kidney demonstrates normal appearance of renal cortex (C), hyperechoic renal sinus (S), and hypoechoic renal pyramids (*arrows*). B. Section through left kidney (LK) on a technically difficult patient shows its relationship to spleen. An ultrasound image of a liver Description automatically generated  C. Transverse section made through midportion of right kidney displays right renal vein (RRV) and proximal ureter (Ur) exiting (*arrow*) renal pelvis. D. Transverse section made through midportion of right kidney (RK, *arrows*); one can identify right renal vein (RRV), inferior vena cava (IVC) responding to inspiration, right renal artery (RRA), aorta (AO), and shadow caused by bowel gas. Anatomic Variants 1. **[Junctional Parenchymal Defect]** Sonographically seen as triangular hyperechoic area anterior aspect of upper pole of right kidney Also known as fetal lobulation which is partial fusion of the ranunculi (embryonic kidney An ultrasound of a fetus Description automatically generated F. Junctional defect: a triangular, hyperechoic area is noted midpole on left kidney (*arrow*) consistent with a junctional defect. 2. **[Hypertrophic Column of Bertin ]** Ultrasound of a baby Description automatically generated Hypertrophied Column of Bertin Longitudinal (G) and transverse (H) sections through the right kidney reveal renal cortex (C, *arrow*) extending toward center into the renal sinus (S). 3. **[Extrarenal Pelvis]** I. Transverse sonogram through midpole of right kidney demonstrates a central anechoic area outside of renal pelvis, but communicating with right kidney consistent with an extrarenal pelvis (P) 4. Dromedary Hump 5. Renal sinus lipomatosis - Urea Nitrogen, Creatinine, uric acid used to evaluate renal function - RBC's, WBC's and bacteria could indicate infection or tumors - Normal values vary based on sex, age, geographic region **[Serum Creatinine-]** - Is a break-down product of skeletal muscle. Creatinine is filtered out of the blood by the kidneys. Serum creatinine threshold levels may vary **[from 1.2 to 2.0 mg/dL depending on the amount of skeletal muscle. ]** Renal arteries and veins best visualized in transverse plane because of perpendicular relationship to sound beam. Right renal vessels best imaged with transducer placed transversely over right kidney and angled medially. Left renal vessels are best imaged with transducer in transverse orientation in midline of abdomen, just inferior to origin of SMA. For kidney visualization, deep inspiration pushes liver, spleen, and kidneys down below the ribs as much as 2.5 cm. Visualizing some portions of liver with right kidney and spleen with left kidney is important to compare echo amplitude to renal parenchyma. - Normal Renal Artery demonstrates continuous forward flow during diastole, typical of low resistance perfusion **[Doppler Exam Techniques:]** - Doppler sample volume should be kept small (2-5mm) - Doppler angle less than 60 degrees between direction of flow and Doppler beam - Set wall filter as low as possible so low velocity info is not hidden - Use smallest possible PRF to minimize error and maximize Doppler tracings **[Resistive Index (RI)]** - Commonly used to evaluate 1- renal transplant rejection, 2-access suspected hydronephrosis, and 3- evaluate renal disease - Renal dysfunction results in a loss of diastolic flow thus an increased renal arterial resistance - **[NORMAL resistive index is usually \< 0.7]** **[RI = peak systolic freq− end diastolic freq]** **[peak systolic freq]** - Hypertension: Longitudinal sections of the left kidney were obtained on a woman with hypertension. - Doppler images presented are the (A) arcuate artery and the (B) interlobar artery. - Data displayed include both peak systolic (V1) and end or minimum diastolic (V2) velocities, systolic/diastolic (S/D) ratio, and resistive index, which are calculated by the equipment. - Agenesis & Hypoplasia - Collecting System Duplications - **Ectopic Kidneys** - Embryologically- kidneys originate in pelvis and ascend into the upper abdomen - Upper pole is more medial than the lower pole of each kidney. Like an inverted 'v' - Congenital anomalies are more common in the genitourinary tract than any other organ system - Complications such as obstruction or stasis associated with congenital abnormalities include: 1. VACTERL -- syndrome 2. MURCS -- syndrome A. Right renal collecting duplication seen as renal parenchyma extends anterior-posteriorly through sinus. Two distinct renal sinuses are seen (*arrows*). B. Different patient: Two dilated ureters are demonstrated exiting the renal hilum suggesting a duplicated system. C. Left duplicated collecting system imaged with display of two left ureteral jets seen in full urinary bladder. - Ectopic kidneys have increased incidence of UPJ obstruction, ureteral reflux, and multicystic renal dysplasia - Can be normal in size or slightly small than normal A. Image of the right upper quadrant demonstrates an empty renal fossa. B. Image of the left upper quadrant reveals an empty renal fossa. C. A single pelvic kidney was found in the left lower quadrant. - Developing kidneys fuse in the pelvis and one kidney ascends to its normal position, carrying the other one with it across the midline - Two kidneys are visualized on one side of the abdomen with absence of a contralateral kidney - In this 53-year-old patient, a small right kidney (D) is fused to the inferior pole of the left kidney (E). - Fusion of upper or most commonly the lower poles across the midline anterior to the aorta - Large "U" shape kidney lies lower in abdomen because ascent is prevented by inferior mesenteric artery. - Ureters are usually located anterior to the isthmus A. Longitudinal image on the right demonstrates a lack of definition of the inferior pole. B. Longitudinal image on the left also demonstrates an indiscernible inferior pole. C. Longitudinal image made over the midabdomen demonstrates the isthmus (*arrows*) anterior to the aorta, representing the inferior pole fusion of both the right and left kidneys. Kidneys Part 2 Cystic renal Masses **[Polycystic Renal Disease]** 1\. Autosomal Dominant Polycystic Kidney Disease (ADPKD) 2\. *Autosomal Recessive Polycystic Kidney Disease (ARPKD) (Pediatric chapter 20)* 3\. *Multicystic Dysplastic Kidney (Pediatric chapter 20)* B. **[Medullary Cystic Disease]** 1\. Medullary Sponge Kidney 2\. Nephronophthisis (Uremic Medullary Cystic Disease) C. **[Cortical Cysts]** 1\. Simple Cysts 2\. Complex Cysts OR Atypical Renal Cysts a\. Hemorrhagic Cysts b\. Infected Cysts c\. Septated or Multilocular Cysts 3\. Calcification(s) in Cysts a\. Calcified Wall b\. Milk of Calcium (MOC) D. **[Parapelvic and Peripelvic Cysts]** E. **[Acquired Cystic Disease]** F. **[Cysts Associated with Systemic Disease]** 1\. Tuberous Sclerosis 2\. von Hippel-Lindau 1. Hereditary in differentiation 2. Non-Hereditary but developmental 3. Acquired disorders Sonography excellent modality for examining type of cystic disease: - **Its an anatomic examination Can distinguish cystic from solid Good for imaging kidneys Portable** - Inherited (\*10% found in spontaneous mutation) - Usually later in life around 4^th^ decade - Bilateral renal enlargement due to development of numerous cysts of varying sizes - Associated with cysts in Liver (50%), Pancreas(10%), and Spleen - Destruction of the residual renal tissue in advanced stages can lead to renal failure and hypertension - Previously known as infantile polycystic kidney disease. This term no longer used... - **Usually present at birth** - **Multiple small cysts throughout kidney** from cystic dilation of the collecting tubules secondary to hyperplasia of the interstitial portions of the ducts - **[Sonographic Findings:]** - Enlarged Kidneys bilaterally - Hyperechoic parenchyma - Loss of cortico-medullary distinction 1. Pulmonary hypoplasia (due to oligohydramnios) 2. Hepatic fibrosis - MCDK is a form of renal dysplasia - Multiple non-communicating cysts with absence of renal parenchyma - Resulting in renal atresia of ureteropelvic junction during development. Typically unilateral but can be bilateral (20%) - Contralateral kidney demonstrates compensatory hypertrophy and in 10% of patients they have ureteropelvic junction obstruction - May persist without any change, may increase in size, or may undergo spontaneous involvement. Kidney progressively involutes and eventually is no longer visible with sonograpahy - Associated with: many syndromes, urinary malformations, and non-renal malformations A. Illustration shows common locations of simple and atypical renal cysts. C. Longitudinal and transverse image displays a simple cyst in medullary region of left kidney. - **[Hemorrhagic cysts]** - **[Infected or Inflammatory cysts]** - Multiple or thick septations - Thick calcifications - Mural nodule/or solid component d\. Longitudinal image demonstrates a renal cyst (C) arising from the inferior pole. e\. This image demonstrates a large simple cyst located on the superior pole (C). f\. Longitudinal image demonstrates a simple cyst in the midpole of the kidney (arrows). **[Parapelvic / Peripelvic Cysts]**  A ultrasound of a baby Description automatically generated **[Parapelvic cyst. A longitudinal section of the right kidney reveals a parapelvic cyst near the inferior pole. Parapelvic cysts should not be confused with dilatation of the renal pelvis.]** **[Acquired Cystic Disease]** - Development of multiple cysts in chronically failed kidneys during long-term dialysis - Hemorrhage often occurs into these acquired renal cysts, resulting in pain and hematuria - Patients undergoing long-term renal dialysis are at an increased risk for acquired renal cystic disease, which predisposes patients to renal cell carcinoma **[Von Hippel-Lindau Disease]** - Inherited disease which usually presents in 2^nd^ -- 3^rd^ decade of life with serious visual impairment - Although Von Hippel Lindau syndrome is characterized by retinal and central nervous system hemangioblastomas, sonographers need to be aware of their related tumors that can be found when performing a complete abdomen exam such as: - Renal Cell Carcinoma, Pheochromocytomas, Islet cell tumors, Renal and Pancreatic cysts - Imaging should be focused on evaluating the kidneys, adrenals glands and pancreas **[Tuberous Sclerosis]** A multi-system genetic disease. Classic presentation include: Seizures, mental retardation, and facial angiofibromas The kidneys are the main focus of an abdominal sonographic evaluation in a patient with tuberous sclerosis. Patients with tuberous sclerosis have an increased incidence of renal cysts and angiomyolipomas. Angiomyolipomas are typically bilateral in patients with tuberous sclerosis.  A. In this 15-year-old male with tuberous sclerosis, multiple hyperechoic angiomyolipomas (*arrows*) were identified in the right kidney. Solid Renal Masses / Neoplasms **[Sonographers Role ]** 1. Location of Mass 2. Distinguish composition of mass 3. Optimize machine settings 4. Document \# of masses 5. Measurements 6. Follow-ups/ document growth 7. Assess Vascularity Benign Neoplasms: 1. Renal Oncocytoma: Renal Oncocytomas ( oxyphilic adenomas) are a type of relatively benign renal tumors. Imaging characteristics of oncocytomas and RCCs overlap, and differentiating an oncocytoma from an RCC and other solid renal neoplasms is not always possible with sonography, CT or MRI. 2. Angiomyolipoma (AML) Also known as **[Hamartoma]**- Mesenchymal mixed tumors composed of fat cells intermixed with smooth muscle cells and aggregates of thick-blood vessels in varying proportions. **[Hyperechoic]** benign renal tumor. Its echogenicity is greater than or equal to that of the renal sinus A **[propagation speed artifact]** may result in the posterior displacement of structures due to the slower acoustic velocity in the fatty mass. CT confirmation of fat in an echogenic renal mass is considered diagnostic angiomyolipoma. 80% involve the right kidney. Longitudinal (B) and transverse (C) images reveal a hyperechoic mass within the midpole of the right kidney. The diagnosis of angiomyolipoma (AML) was made. A small hyperechoic lesion within the renal parenchyma demonstrates the classic sonographic appearance of an angiomyolipoma. The mass is very echogenic, homogeneous, and well circumscribed. Other Benign Renal Tumors 1. **Lipoma** 2. **Leiomyoma** 3. **Juxtaglomerular tumor (reninoma)** 4. **Hemangioma** 5. **Fibroma** 6. **Multilocular cystic nephroma** 7. **Adenoma** Renal Cell Carcinoma (RCC) AKA: **[Hypernephroma]** or **[adenocarcinoma]** of kidney Most common solid renal mass in the adult Often unilateral encapsulated mass. More common in males **[Sonographic Findings:]** Most often Hypoechoic relative to the normal adjacent renal parenchyma although it may appear hyperechoic **[Signs & Symptoms:]** **[Hematuria is]** Most Common and significant finding. May have pain and palpable mass **[Increased Incident associated with :]** - Acquired cystic disease (chronic dialysis) - Von Hippel-Lindau Syndrome - Tuberous sclerosis ADP **[Wilms Tumor Nephroblastoma)]** AKA- **[Nephroblastoma]**- Most common **[CHILDHOOD]** renal tumor. Mean age diagnosis is 3.5 years. Patients typically present with a large asymptomatic flank mass. Other symptoms include Hypertension, fever, and hematuria \*Metastasis can be seen in lungs, liver, bone, lymph nodes, and retroperitoneum. Tumor extension can be seen into the renal vein and inferior vena cava. Wilm's tumors must be differentiated from adrenal neuroblastomas. Wilm's tumors destroy the renal contour. If normal renal contour is maintained bilaterally, an abdominal mass is most likely an adrenal neuroblastoma. Associated with **[Beckwith-Weidemann Syndrome ]** Urothelial Carcinoma **Urothelial tumors** are malignant tumors of the lining of the renal pelvis, calyces, ureter, and bladder **[Transitional Cell-]** most common bladder neoplasm. **[Squamous Cell-]** account for about 10% of urothelial carcinomas **[Transitional Cell Carcinoma(TCC)-]** urinary tract lined with transitional cells. TCC commonly in bladder-bladder mass Hydronephrosis may be caused by TCC **[Hematuria]** is the most common clinical presentation of TCC. A ultrasound of a fetus Description automatically generated An x-ray of a person\'s body Description automatically generated Urothelial Carcinoma--Transitional Cell Carcinoma Longitudinal (A) and transverse (B) of a 79-year-old woman's right kidney reveal a hypoechoic mass located within the renal sinus. C. CT confirms the presence of a mass in the renal pelvis. Appearance and location are consistent with transitional cell carcinoma. **[Metastatic Renal Tumors- Lymphoma]** Renal Parenchyma may be a site of secondary tumors that have metastasized from other primary organs such as lung, breast, colon... Malignant cells from leukemia and lymphoma can also metastasize to kidneys **[Sonographic Findings:]** - Hypoechoic masses or - Diffusely enlarged inhomogeneous kidney **[Dilation of the renal collecting system]** - [**Caliectasis**-] dilation of calices - **Pelciectasis-** dilation of renal pelvis - **Pelvicaliectasis**- dilation of calices and renal pelvis **Causes:** - **Intrinsic:** *calculi, UPJ obstruction, tumors* - **Extrinsic**: *Neoplasm,* trauma, surgery, *BPH,* neurogenic bladder, *GYN* bladder outlet, *Pregnancy,* obstruction, *Prostate CA* - Grade I / Mild - Grade II / Moderate - Grade III / Marked or Severe *If left untreated, Hydronephrosis secondary to obstruction can lead to Hypertension, loss of renal* *function and Sepsis*  Diagram of different stages of kidney disease Description automatically generated **Grade 1 mild of HYRDO** **61-year-old woman presented with bilateral flank pain. Longitudinal images of right kidney (B) and left kidney (C) demonstrate mild distortion of pelvocaliceal structures with dilated fluid-filled calyces.** **D: Different with grade I with mild separation of renal pelvis.\ ** **GRADE 2 HYRDRO/ MODERATE** **Grade II Hydronephrosis** **E,F: Dilated calyces and renal pelvis on two different patients.** **GRADE 3/MARKED SEVERE** **Grade III Hydronephrosis** **An 82-year-old woman evaluated for frequent urinary tract infections.** **G: On longitudinal and (H) transverse sections of right kidney, there is dilatation of pelvis, calyces, and proximal ureter.** **Urolithiasis (*arrows*) is noted within the proximal ureter in both images.** **[LITHIASIS ]** **[Urolithiasis-]** Calculi that can develop anywhere in the urinary system Most develop in the kidney (nephrolithiasis) Symptoms depend on the location and size of the calculi Can be difficult to see and discern a shadow due to highly reflective echoes of kidneys sinus **[Types of Calculi:]** Some form of calcium, uric acid, struvite or magnesium ammonium phosphate, crystine, **[Nephrocalcinosis]** **[Renal parenchymal calcium deposits]**. Occurs in **[cortical or medullary]** or both regions. Calcium levels are increased and often this is detected through x-ray as incidental finding. Usually bilateral and diffuse **[Nephrolithiasis- Renal Stones]** **[Arise in the collecting system]** Main symptom is acute back or flank pain often radiating down to ipsilateral groin. When severe- can have fever, chills, dysuria, cloudy urine and hematuria Nephrolithiasis (kidney stones)  C:\\Users\\TEMP.S4CARLISLE\\Desktop\\PPT JPEG\\Chapter 04\\Kawamura-ch010-image024ad copy 2.jpg  An arrow pointing to a liver Description automatically generated 42-year-old woman presented with hematuria. Longitudinal image of the right kidney reveals multiple hyperechoic foci (*arrows*) representative of renal calculi. There is acoustic shadowing due to the attenuation of sound by the stone. A. A color Doppler image of the same patient demonstrates the twinkle artifact (*arrows*) posterior to the stones. C. Nephrolithiasis D. A 24-year-old woman presented with left lower quadrant pain. E. \(A) Longitudinal and (B) transverse sections of the right kidney (RK) demonstrate a single hyperechoic focal lesion (*arrow*) representing nephrolithiasis. F. Acoustic shadowing is seen posterior to the calculi. A 40-year-old man presented with hematuria. Sonography evaluation of the left kidney reveals a **[staghorn calculus]** filling the renal sinus. **H**. Longitudinal section of left kidney demonstrates a strong acoustic shadow emanating from the renal sinus. Transverse sections through (**I**) superior, Nephrolithiasis A. Fusion image demonstrates a sonogram (*left image*) of the right kidney with multiple renal calculi (*arrows*) in the inferior pole. The CT (*right image*) demonstrates two renal calculi. **[Twinkle Artifact]** A. A gray-scale image of a kidney with an echogenic area (*arrow*) creating minimal shadowing in the midpole. B. Color Doppler shows a mix of colors posterior to the hyperechoic area, confirming the diagnosis of nephrolithiasis. Nephrocalcinosis Nephrocalcinosis Longitudinal images of the right (A) and left (B) kidneys reveal multiple hyperechoic medullary calcifications and a normal renal cortex (C). Nephrocalcinosis is usually related to abnormal metabolic states leading to hypercalcemia. **[RENAL TRAUMA ]** [Renal Trauma] - Blunt (70%) Sports trauma, work, mva - Penetrating: Gunshot, stab wounds - Contusions, lacerations - Renal fracture - Ct examination of choice in trauma cases. FAST very useful - Main vessel rupture, shattered kidneys UPJ destruction Vascular Trauma-Hematoma A. Longitudinal image reveals irregular hypoechoic area (*arrows*) on the superior pole of the kidney in a patient who experienced blunt trauma. B. Power Doppler indicates no flow in hypoechoic area (*arrows*). Based on the clinical and sonographic information, the diagnosis of hematoma was made. **[HEMATOMAS]** **Causes:** Spontaneous and posttraumatic **Spontaneous:** RCC, AML, segmental renal infarction, AV malformation, hemorrhagic cyst. Posttraumatic intrarenal hematomas result from biopsy, bleeding diathesis (result from blood thinners medication); necrotizing arteritis, hemophilia. **Depending on age hematomas have varying echo patterns**. May go from anechoic, complex, echogenic, then reverted back to anechoic. **Subcapsular hematoma** lies between the renal cortex and the capsule Vascular Trauma--Subcapsular Hematoma A 24-year-old patient with a history of blunt abdominal trauma. C. Longitudinal image of the left kidney demonstrates a hypoechoic collection anterior to the kidney (*arrows*). Collection lies between echogenic renal capsule and renal cortex. Hematoma follows the kidney contour. D. Transverse image demonstrates fluid collection anterior to the kidney **[Infarction]** Caused by blood supply obstruction of the artery (By embolism coming from heart or aorta) or by occlusion or stenosis of the vein drainage. Immediately after an infarction it is difficult to characterize with sonography. **[Within 24 of arterial occlusion the infarcted area often looks hypoechoic.]** **[With increased time this area will look echogenic.]** **[RENAL INFECTION AND INFLAMMATION ]** They are rather common clinical problem and include glomerulonephritis, acute tubular nephritis, and pyelonephritis( renal pelvis). The exact type depends on the type of bacteria involved and the portion of the kidneys affected ACUTE PLYONEPHRITIS Results from bacterial invasion of renal parenchyma Most renal infections occur via an ascending route from the bladder. Usually caused by gram-negative bacilli from intestinal tract. Imaging studies are not necessary because diagnosis van be made clinically. *If infection is **[focal]** it is called acute focal bacterial nephritis or lobar nephronia. Ultrasound shows a focal wedge-shaped area or hypoechoic renal lobe. Similar to ischemia or infarction.* **[Sonographic Findings:]** Renal enlargement Hypoechoic parenchyma Absence of sinus echoes Acute Pyelonephritis (APN) A 60-year-old woman presented with severe urosepsis. Longitudinal (A) and transverse (B) sections through the right kidney reveal a swollen, hypoechoic, heterogeneous right kidney. C. CT demonstrates enlargement of the right kidney and a normal left kidney. Emphysematous Pyelonephritis A bacterial infection associated with renal ischemia. More commonly occurring : Diabetics (87 -- 97% of patients) Immunosuppressed patients and patients with urinary tract obstructions. **[Anerobic bacteria produce intrarenal gas causing reverberation or comet-tail artifacts.]** Nephrectomy is usually required to treat infection Emphysematous Pyelonephritis (EPN) A. Longitudinal sonogram reveals gas within the renal parenchyma (*open arrow*). B. Follow-up longitudinal coronal sonogram performed 2 weeks later after therapy with intravenous antibiotics reveals improvement, although there is still some gas (*arrow*) within the renal cortex. **Chronic Pyelonephritis Xanthogranulomatous Pyelonephritis (XGP**) **[Chronic Pyelonephritis: ]** Renal injury induced by recurrent renal infection due to: Anatomic anomalies, obstructive lesions, ureteral reflux **[Sonographic Findings:]** Leading to end-stage renal disease- appears small and hyperechoic with cortical thinning. **[XGP-]** type of chronic pyelonephritis results from chronic infections due to long term obstruction. Rare **[Associated findings:]** renal enlargement, parenchymal abscesses, staghorn calculus, papillary necrosis, hydronephrosis, pyonephrosis, loss of cortical-medullary boundary, cortical thinning Renal examination on a pregnant patient. A. Sonogram of right kidney (RK) demonstrates two hyperechoic focal calcifications (*arrows*) seen in renal sinus (s) and hypoechoic areas (open arrows) representing abscess seen in renal cortex. B. CT: multiple poorly defined low-density areas (*arrows*) are identified within renal parenchyma. Patient's history and sonography and CT appearances are consistent with XGP. **[Pyonephritis & Fungal Infections]** **[Pyonephrosis]**- purulent material in collecting system Percutaneous or surgical drainage required to treat. Shown as hyperechoic debris in dilated collecting system **[Fungal Infections-]** candida is most common cause of fungal infections worldwide. If obstructive- **[fungal ball]** appears as **[hyperechoic nonshadowing mass]** Pyonephrosis The longitudinal images of these two patients diagnosed with pyonephrosis display (A) focal pyonephrosis (*arrows*) and (B) pyonephrosis affecting the entire enlarged kidney. Fungal Infections A. This patient presented with *Pneumocystis jiroveci* pneumonia. The sonogram displays an enlarged, infected kidney (*arrows*) with abnormal echogenicity. Fungal Infections B,C: Images are a 3-week-old premature girl who had surgery for peritonitis and bowel rupture. Postsurgical complications included fever, elevated ALT, AST, and alkaline phosphatase, leukocytosis, and pyuria. Sonography examination of urinary system demonstrated kidneys of normal size and shape with echogenic masses appearing in both. On longitudinal (B) and transverse (C) images, loculated, echogenic, nonshadowing masses (*arrow*) are seen in the right kidney (RK; KID, arrowheads). Largest measured 5 mm. Other findings included a markedly enlarged liver and fluid collections. Patient was diagnosed with fungal infection and was treated with antibiotics. Sonography follow-up within 2 weeks demonstrated less conspicuous fungus balls. Follow-up within 1 month demonstrated normal renal architecture. RENAL INJURY **[Renal Injury Classified as:]** - **[Acute-]** develops several days or weeks - **[Chronic-]** spans months or years - **[Acute on chronic-]** rapid reduction in renal function in patients with previously stable chronic disease - **[Renal Injury]** is the ability of the kidneys to remove accumulation of metabolites from the blood. - Causes alteration in electrolyte, acid-base, and water balance - Underlying causes vary and include: - renal pathology, systemic disease, urogenic defects of non renal origin attributed to surgery or trauma, pregnancy, nephrotoxitcity - Acute Kidney Injury (AKI) - B. Chronic Kidney Disease (CKD) - C. Dialysis Patient - 1\. Complications - a\. Acquired Cysts. b. Renal Tumors [Acute Kidney Injury AKI] **3 Main Mechanisms of AKI:** 1. **Prerenal Failure (inadequate perfusion):** Hypotension, volume decreased cardiac output 2. **Intrinsic Renal Failure:** Acute tubular necrosis, acute glomerulonephritis, nephrotoxins 3. **Postrenal Failure (obstructive nephropathy):** obstructive tubules with precipitates, bilateral ureteral obstruction, bladder outlet obstruction, bilateral renal vein thrombosis Previously called acute renal failure (ARF) Rapid decrease in renal function Suspected when urine output falls or BUN and creatinine levels rise. Most common cause is **[Acute Tubular Necrosis]** **[Sonography's Role:]** - **[Hydronephrosis-]** Indicates postrenal failure - **[Abnormal RI-]** suggests intrinsic - **[Labs:]** urine output, urinalysis, BUN, serum creatinine Acute Kidney Injury (AKI) An 86-year-old woman was diagnosed with acute renal failure based on clinical presentation and laboratory results. The longitudinal section of the (A) right kidney (RK) reveals hydronephrosis whereas the (B) left kidney (LK) is small with increased cortical echogenicity and a small kidney measuring 8.6 cm in length. [Chronic Kidney Disease End-Stage Kidney Disease] Previously Chronic Renal Failure Irreversible condition Diminished function of nephrons- decreased GF, renal blood flow, tubular function, and resorptive capability. **[Sonographic Findings:]** Not disease specific Small, echogenic, shrunken kidney **Treatment:** Dialysis or renal transplant necessary when management is not effective Chronic Kidney Disease (CKD) Longitudinal sections of (A) right kidney and (B) left kidney demonstrate small, hyperechoic kidneys in this patient with a history of chronic renal failure. **[Renal tumors-]** a complication of dialysis patients with acquired cystic disease Acquired cystic disease of the kidneys, dialysis related. **[Acquired Cysts]** is a common **[complication]** with CKD patients receiving hemodialysis. Develop bilateral cystic disease Cysts located throughout kidney and involve cortex, corticomedullary junction and medulla. Kidneys often appear small and echogenic Longitudinal images of the (A) right and (B) left kidneys reveal shrunken, echogenic, bilateral kidneys (*arrows*) consistent with chronic renal failure. Multiple small bilateral cysts are seen in this hemodialysis patient. **[RENAL TRANSPLANTS ]** - Renal transplantation is the treatment of choice for end-stage renal disease - Diabetes is the most common cause of renal disease leading to kidney transplantation - Pretransplant evaluation of the living donor is important for screening and surgical planning. - Harvesting the left kidney is favored due to its longer renal vein - Multiple renal arteries need to be identified as this will require additional surgical time - The transplanted kidney can be placed on either side of the pelvis. - The ureter is attached to the urinary bladder - The arterial anastomosis may be with the external or internal iliac artery - Poor function of the renal transplant may be the result of acute tubular necrosis (ATN) in the immediate posttranplantation period. **[Sonography utilized in assessing:]** Immediate surgical complications Location for renal biopsy Vascular status in acute rejection **Sonographic findings of acute transplant rejection:** Renal enlargement (increased length) Decreased kidney echogenicity Loss of cortical medullary boundary Increasing flow resistance (RI) **[Post-Transplant Complications:]** - **[Fluid Collections: ]** Hematomas (24 hrs post-op) Urinomas (24 hrs post-op) Lymphoceles Abscesses - **[Renal artery kinking or thrombosis]** - **[Renal vein thrombosis]** - **[Resistive Index]** - **Used to evaluate arterial flow resistance of the renal vascular bed** - **\< 0.7 = normal resistive index** - **.07 -.08 = questionable transplant dysfunction** - **\> 0.8 = transplant dysfunction** RENAL VASCULAR ABNORMALITIES **The normal renal artery demonstrates continuous forward flow during diastole, typical of low resistance perfusion.** 1. **Renal artery stenosis** **[Symptoms:]** **Sudden onset of hypertension** **Uncontrollable hypertension** **[Methods & Criteria:]** **[Direct evaluation-] Renal artery velocities** **Renal artery/Aorta ratio (RAR) \>3.5** **[Indirect evaluation-] Intrarenal waveform eval.** **Parvus Tardus** **Absent early systolic peak** ***Parvus Tardus is defined as a small slow pulse*** **2Renal artery thrombosis (occlusion)** Renal artery thrombosis (Occlusion) is a sudden cause of prerenal failure that presents as: - Acute flank pain - Hematuria - Sudden rise in BP **[Sonographic Findings:]** - Focal Hypoechoic areas of Infarct - Absence of intrarenal arterial flow - Renal enlargement 3. **Renal artery aneurysm** 4. **Renal vein thrombosis** - Nephrotic syndrome - Hypercoagulability disorders - Malignant renal tumors - Extrinsic compression - Trauma - Dilated thrombosed renal vein - Absent intrarenal venous flow - Enlarged hypoechoic kidney - High-resistance renal artery waveform (increased RI) - What is the most common ***solid renal mass*** is ***adult***? - **[Renal Cell Carcinoma]** - What is the most common ***childhood renal mass***? - **[Wilm's tumor]** - What is the most common ***neonatal solid renal tumor***? - **[Mesoblastic Nephroma]** - What is the most common ***neonatal abdominal mass***? - **[Multicystic Dysplastic Kidney]** - What is the most common ***neonatal adrenal mass*** (in newborns) - **[Adrenal Hemorrhage]** - What is the most common ***childhood adrenal mass***? - **[Adrenal Neuroblastoma]** - Kidneys are part of superior urinary system - Ureter, bladder, and urethra form lower urinary system and play important roles in transporting, storing, and eliminating urine - Pelvic ureter and urethra are conduits in process of elimination of urine - Urinary bladder is located anatomically between ureter and urethra and functions as a reservoir for urine storage