1- Urinary obstruction and stasis

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary consequence of urinary tract obstruction on renal function?

Permanent renal damage (correct)

Improved electrolyte balance

Increased renal perfusion pressure

Enhanced glomerular filtration rate

Which of the following factors directly influences glomerular filtration rate (GFR)?

Blood pH levels

Patient age

Hydronephrosis severity

Renal plasma flow (correct)

In the context of obstructive uropathy, what does the term 'unilateral obstruction' refer to?

Complete blockage of the renal pelvis

Obstruction affecting both kidneys

Obstruction at the distal urethra only

Obstruction localized to one kidney (correct)

How does renal plasma flow (RPF) relate to the overall pressure in the renal system?

RPF increases as resistances in the arterioles decrease Signup and view all the answers

What is a key difference between unilateral and bilateral ureteral obstructions?

Bilateral obstruction affects distribution of renal blood flow Signup and view all the answers

What does hydronephrosis indicate in relation to urine flow?

Dilation of renal pelvis or calyces Signup and view all the answers

What is the glomerular ultrafiltration coefficient (Kf) primarily affected by?

Renal blood flow Signup and view all the answers

Which of the following defines obstructive uropathy?

Functional or anatomic obstruction in urinary flow Signup and view all the answers

What is the impact of temporary obstruction on GFR?

GFR may decrease but can recover once the obstruction is relieved Signup and view all the answers

Which pressure is NOT a determinant of glomerular filtration rate (GFR)?

Blood pressure in systemic circulation Signup and view all the answers

What gross pathologic finding is observed at 7 days after urinary obstruction?

The cortex remains slightly enlarged Signup and view all the answers

Which microscopic finding is characterized by widespread damage after 5 to 6 weeks of obstruction?

Tubular atrophy and glomerular collapse Signup and view all the answers

What is a key characteristic of post-obstructive diuresis after the relief of urinary tract obstruction?

Urine outputs may reach 200 mL/hr or greater Signup and view all the answers

What does the renal pelvis and ureter demonstrate 42 hours after obstruction?

Dilation of the pelvis and ureter Signup and view all the answers

What histological change occurs in the collecting system due to obstruction at 5 to 6 weeks?

Proliferation of connective tissue Signup and view all the answers

What is the expected appearance of totally obstructed kidneys after 6 weeks?

They exhibit a cystic appearance and are enlarged Signup and view all the answers

Which factor does NOT contribute to the pathological changes observed during renal obstruction?

Presence of renal stones Signup and view all the answers

What happens to the collecting ducts' responsiveness to ADH after urinary obstruction?

Poor responsiveness to ADH occurs post-obstruction Signup and view all the answers

What is a significant renal change seen at 21 to 28 days after obstruction?

Thinning of cortex and medullary tissue Signup and view all the answers

What occurs during the first phase of unilateral ureteral occlusion (UUO)?

RBF increases alongside high renal tubular and collecting system pressure. Signup and view all the answers

How does renal blood flow (RBF) change in bilateral ureteral occlusion (BUO) after the initial phase?

RBF sees a slight increase before a profound decline. Signup and view all the answers

What is a key difference in ureteral pressure between unilateral and bilateral ureteral occlusion?

Ureteral pressure remains elevated for 24 hours in BUO. Signup and view all the answers

What characterizes the hemodynamic change during the second phase of UUO?

RBF begins to decline while ureteral pressure remains elevated. Signup and view all the answers

What role do prostaglandins and nitric oxide (NO) play in UUO?

They are responsible for initiating renal vasodilation. Signup and view all the answers

After the release of obstruction in BUO, what is significantly greater compared to UUO?

The postobstructive diuresis. Signup and view all the answers

During the third phase of UUO, what happens to RBF and ureteral pressure?

Both RBF and ureteral pressure decline together. Signup and view all the answers

How does intrarenal blood flow distribution differ between UUO and BUO?

It shifts towards outer cortex in UUO. Signup and view all the answers

What is the primary mechanism contributing to early vasoconstriction during BUO?

The lack of early renal vasodilation. Signup and view all the answers

Which physiological change is NOT associated with both UUO and BUO?

Normalization of intratubular-ureteral pressure. Signup and view all the answers

What condition is marked by an inflammatory mass that can potentially obstruct ureters?

Retroperitoneal Fibrosis Signup and view all the answers

Which factor contributes to the development of hydronephrosis during pregnancy?

Hormonal changes Signup and view all the answers

What is a common complication associated with tubo-ovarian abscess?

Anuria Signup and view all the answers

What is the mechanism by which progesterone contributes to hydronephrosis during pregnancy?

Ureteral dilatation Signup and view all the answers

What rare condition involves an exuberant overgrowth of nonmalignant adipose tissue in the pelvic region?

Pelvic Lipomatosis Signup and view all the answers

What vascular issue may present with signs of ureteral obstruction due to its mass effect?

Abdominal Aortic Aneurysm Signup and view all the answers

Which method can resolve ureteral obstruction caused by a tubo-ovarian abscess?

Antibiotic therapy Signup and view all the answers

What percentage of women of reproductive age may experience endometriosis?

10% to 20% Signup and view all the answers

What occurs in the renal system during pregnancy that may lead to hydronephrosis?

Ureteral compression by the enlarged uterus Signup and view all the answers

What complication can arise due to a vascular mass effect from an abdominal aortic aneurysm?

Decreased urine output Signup and view all the answers

Study Notes

Urinary Obstruction and Stasis

Urinary tract obstruction can occur during fetal development, childhood, or adulthood.
Obstruction location can be proximal (calyces) or distal (urethral meatus).
Renal obstruction leads to permanent damage, limiting metabolic waste excretion, and altering water and electrolyte balance.

Renal

Congenital: Polycystic kidney, renal cyst, peripelvic cyst, ureteropelvic junction obstruction, Wilms tumor
Neoplastic: Renal cell carcinoma, transitional cell carcinoma of the collecting system, multiple myeloma
Inflammatory: Tuberculosis, Echinococcus infection
Metabolic: Calculi, sloughed papillae
Miscellaneous: Trauma, renal artery aneurysm

Bladder and Urethra

Congenital: Posterior urethral valve, phimosis, hydrocolpos
Neoplastic: Bladder carcinoma, prostate carcinoma, carcinoma of urethra, carcinoma of penis, paraurethral abscess, neurogenic bladder
Inflammatory: Prostatitis
Miscellaneous: Benign prostatic hypertrophy

Definitions

Hydronephrosis: Dilation of the renal pelvis or calyces, often associated with obstruction, but can be present without it.
Obstructive uropathy: Functional or anatomic obstruction of urinary flow at any level of the urinary tract, leading to functional or anatomic renal damage.

Global Renal Functional Changes

Functional changes associated with obstructive nephropathy include changes in renal hemodynamic variables and glomerular filtration.
These changes are influenced by the extent and severity of the obstruction, whether unilateral or bilateral, and whether the obstruction persists or has been relieved.

Factors Influencing GFR

GFR (glomerular filtration rate) is expressed as GFR = Kf (PGC − PT − πGC):
- Kf: glomerular ultrafiltration coefficient
- PGC: glomerular capillary pressure (influenced by renal plasma flow (RPF) and arteriolar resistance)
- PT: hydraulic pressure of fluid in the tubule
- πGC: oncotic pressure of proteins

Renal Plasma Flow (RPF)

RPF depends on renal perfusion pressure and intrarenal resistance to flow, primarily mediated by resistances in the afferent and efferent arterioles.
- RPF = aortic pressure – renal venous pressure – renal vascular resistance
Obstruction can temporarily or permanently alter GFR and its determinants.

Unilateral vs. Bilateral Ureteral Obstructions

Unilateral and bilateral ureteral obstructions differ in the patterns of hemodynamic changes, ureteral pressure changes, and distribution of renal blood flow.

Hemodynamic Changes with Unilateral Ureteral Occlusion (UUO)

UUO demonstrates a triphasic pattern of RBF and ureteral pressure changes:
- Phase 1 (1-2 hours): Increased RBF and high PT/collecting system pressure.
- Phase 2 (3-4 hours): Elevated pressure parameters, declining RBF.
- Phase 3 (5+ hours): Further decline in RBF and decrease in PT/collecting system pressure.

Hemodynamic Changes with Bilateral Ureteral Occlusion (BUO)

BUO results in a modest increase in RBF lasting about 90 minutes, followed by a prolonged and more significant decline in RBF than in UUO.
Intrarenal blood flow distribution is different in BUO compared to UUO.
Ureteral and tubular pressures are elevated for the first 4-5 hours, remain elevated for at least 24 hours with BUO, and approach pre-occlusion levels after 24 hours in UUO.

Summary of UUO and BUO

Both involve increases in renal vascular resistance and ureteral pressure.
Timing and regulation differ.
UUO: initial vasodilation (prostaglandins/NO), followed by prolonged vasoconstriction, and normalization of pressure.
BUO: little initial vasodilation, more profound vasoconstriction; postobstructive diuresis is greater due to volume expansion, urea, osmolytes, and ANP.

Pathologic Changes of Obstruction

Pathologic changes are affected by infection presence/duration, and intra/extrarenal localization.

Gross Pathologic Findings

Findings at varying post-obstruction time points (42 hours, 7 days, 12 days, 21/28 days, 6 weeks) include dilation of the pelvis/ureter, blunting of papillary tips, increased renal weight, edema, cortical enlargement, increased calyceal dilation, and thinned cortex/medullary tissue.

Microscopic Pathologic Findings

Findings include widespread glomerular collapse and tubular atrophy, interstitial fibrosis, and proliferation of connective tissue in the collecting system (5-6 weeks after obstruction) with a cell-poor stroma composed of elastic and collagen fibers in the renal interstitium in obstructed portions.

Electron Microscopic Pathologic Findings

Electron microscopy shows tubular atrophy, glomerular collapse, and renal pelvic smooth muscle atrophy.
Obstructed portions of the collecting system demonstrate other changes, including a cell-poor stroma composed of elastic and collagen fibers.

Post Obstructive Diuresis

Relief of obstruction results in significant polyuria (urine outputs of 200 mL/hr or greater).
Occurs primarily in bilateral obstruction (BUO), often self-limiting, and rarely occurs with contralateral normal kidney.

Post Obstructive Diuresis Mechanisms

Downregulation of sodium transporters contributes to the saline diuresis.
Increased ANP and other natriuretic peptides play a role.
Poor responsiveness of collecting duct to ADH (due to downregulation of aquaporin water channels) contributes.

Selected Extrinsic Causes of Ureteral Obstruction

Retroperitoneal Fibrosis: Fibrotic/inflammatory mass envelops retroperitoneal structures, potentially obstructing ureters.
Pelvic Lipomatosis: Rare benign condition of pelvic adipose tissue overgrowth, potentially causing ureteral obstruction.

Obstetric and Gynecologic

Pregnancy: Hydronephrosis is common during pregnancy (43-100% occurrence), often resolving within 6 weeks postpartum; hormonal (progesterone) and mechanical (uterus compression) factors contribute.

Benign Pelvic Abnormalities

Tubo-ovarian Abscess: Tubo-ovarian abscess, often associated with PID, may cause extrinsic ureteral obstruction, possibly leading to anuria, treatable with antibiotic therapy, transvaginal drainage, open/laparoscopic intervention, internalized ureteral stents or percutaneous nephrostomy.
Endometriosis: Defined by endometrial tissue in ectopic locations, affects 10-20% of reproductive-age women, peaking in the mid-20s; potential for malignant transformation.

Vascular Obstruction

Abdominal Aortic Aneurysm (AAA): Signs of AAA may be initial manifestation of ureteral obstruction (due to mass effect or localized inflammation).
- Ureteral deviation may occur (pushed laterally or medially, with possible obstruction associated with desmoplastic reaction of inflammatory aneurysms or IAAA).
- Close monitoring is necessary with stent placement or an endovascular approach for possible recurrent or de novo ureteral obstruction.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores urinary tract obstructions including their locations, causes, and potential consequences. Covering both congenital and acquired conditions, you will learn about various renal and bladder pathologies, their impacts on health, and the importance of timely diagnosis. Assess your understanding of these critical topics in urinary health.