Principles and Acute Management of Upper Urinary Tract Obstruction PDF

24Principles and Acute Management of Upper Urinary Tract Obstruction MICHAEL S. BOROFSKY AND ROBERT M. SWEET CONTRIBUTORS OF CAMPBELL-WALSH-WEIN, 12TH EDITION Casey A. Dauw, Stuart J. Wolf, Craig A. Peters, and Kirstan K. Meldrum CLINICAL PRESENTATION Upper urinary tract obstruction refers to...

24Principles and Acute Management of Upper Urinary Tract Obstruction MICHAEL S. BOROFSKY AND ROBERT M. SWEET CONTRIBUTORS OF CAMPBELL-WALSH-WEIN, 12TH EDITION Casey A. Dauw, Stuart J. Wolf, Craig A. Peters, and Kirstan K. Meldrum CLINICAL PRESENTATION Upper urinary tract obstruction refers to the blockage of urinary flow from the renal calyces to the level of the ureterovesical junc- tion. It is distinct from lower urinary tract obstruction (i.e., blad- der through urethra); however, it can occur secondarily to lower urinary tract obstruction or dysfunction (i.e., urinary retention). Proper functioning of the lower urinary tract should always be considered in the differential. Upper urinary tract obstruction can have a variable presentation. It can be symptomatic or asymptomatic, acute or chronic, and uni- lateral or bilateral, and it has a broad differential diagnosis. Obstruc- tive uropathy accounts for approximately 10% of all cases of renal failure. On a population level, hydronephrosis tends to be more prevalent in women ages 20–60 years owing to pregnancy and gyne- cologic malignancies. After the age of 60 years, men are more likely to have hydronephrosis owing to the presence of prostatic diseases. The most common presenting symptom associated with acute upper urinary tract obstruction is flank pain owing to stretching of the renal capsule. This can radiate to the lower abdomen, testicles, or labia and can cause severe degrees of discomfort along with nausea and vomiting. Chronic upper urinary tract obstruction, on the other hand, tends to have a milder course and in some cases can be painless. 616 Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 617 Upper urinary tract obstruction can be associated with renal functional damage, particularly if left untreated. This is particu- larly concerning when present in childhood because congenital obstruction can prevent the kidneys from normal development. Acquired obstruction can similarly be determinantal to existing renal function in the mature adult as well. HEMODYNAMIC CHANGES Ureteral obstruction can lead to numerous functional changes that affect renal hemodynamics. Such changes depend on whether the obstruction is unilateral or bilateral. There is a triphasic response of renal blood flow in unilateral ureteral obstruction. In phase 1 (initial 2 hours), there is an increase in renal tubular pressure as a result of obstruction, leading to a decrease in glomerular filtration rate (GFR). The renal vasculature attempts to compensate for this de- crease in GFR by increasing renal blood flow mediated by the re- lease of vasodilators such as prostaglandin E2 and nitric oxide. During phase 2 (6–24 hours), the ureteral pressure remains elevated, and renal blood flow diminishes. In phase 3 (.24 hours), renal pelvic pressures trend down but remain elevated, and renal blood flow continues to diminish (Fig. 24.1), leading to renal ischemia. In the case of bilateral ureteral obstruction (or solitary kidney obstruction), there is only a modest initial increase in renal blood flow followed by a more rapid decline, which can exacerbate the potential for renal function damage (Fig. 24.2). This is of clinical importance because timely decompression is of the essence. FUNCTIONAL CHANGES Upper urinary tract obstruction can damage the kidneys in several ways. Some of the functional change can be transient and relieved when the pressure is relieved; however, there is also the potential for permanent damage in cases with longstanding obstruction if associated with high pressures. It is likely that the risk of perma- nent damage to the affected kidney is related to the duration, degree, and severity of obstruction, though this these parameters are poorly defined. One unique functional sequelae that occurs upon relief of bilat- eral ureteral obstruction or obstruction in a solitary kidney is postobstructive diuresis. This condition refers to polyuria that occurs as a result or in relation to osmotic diuresis of accumulated Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 618 CHAPTER 24 Principles and Acute Management Mean left ureteral pressure 60 ± Standard error 55 n=5 50 (mm Hg) 45 40 35 30 25 20 I II III 6.0 Mean left renal blood flow 5.0 4.0 (mL/g/min) 3.0 2.0 1.0 L Ureter obstructed 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Control Time in hours FIG. 24.1 Triphasic relationship between ipsilateral renal blood flow and left ureteral pressure during 18 hours of left ureteral obstruction. The three phases are designated by Roman numerals and separated by vertical dashed lines. In phase I, renal blood flow and ureteral pressure rise together. In phase II, the renal blood flow begins to decline, and ureteral pressure re- mains elevated. In phase III, the blood flow and ureteral pressure decline together. (From Moody TE, Vaughan ED JR, Gillenwater JY. Relationship be- tween renal blood flow and ureteral pressure during 18 hours of total ureteral occlusion. Implications for changing sites of increased renal resistance. Invest Urol 1975;13:246-251.) solutes, impaired tubular concentrating ability and reabsorption, as well as an increase in production of atrial natriuretic factor (ANP), which stimulates sodium wasting. Although this condition is typically self-limited, it is important to monitor electrolytes and ensure that the patient can self-hydrate to account for the potential of excess fluid losses. This condition is unlikely to occur in the Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 619 Bilateral obstruction or Unilateral obstruction solitary kidney RBF: Rafferent Acute RBF: Rafferent phase ~ GFR: Ptubule Rafferent 1–2 hours GFR: Ptubule Rafferent Changes mediated by increase in vasodilators: NO, PGE2 Mid RBF: Rafferent RBF: Refferent phase GFR: Ptubule Rafferent 2–5 hours GFR: Ptubule RBF: Rafferent Late RBF: Refferent phase GFR: Ptubule Rafferent 24 hours GFR: Ptubule Changes mediated by Changes mediated by decrease in NO increased ANP FIG. 24.2 Summary of the functional changes during ureteral obstruction. ~, Little change; ANP, atrial natriuretic peptide; GFR, glomerular filtration rate; NO, nitric oxide; PGE2, prostaglandin E2; Ptubule, tubular hydrolic pressure; Rafferent, afferent arteriolar resistance; RBF, renal blood flow; Refferent, efferent arteriolar resistance. setting of a normal contralateral kidney, which would otherwise be expected to maintain fluid and electrolyte balance. DIAGNOSIS AND TESTING Laboratory Studies Urinalysis. Can provide an estimation of osmolality, evidence of urinary tract infection, insight into stone formation based on crys- tals that may be present in the urine, and the possible presence of medical renal disease with the presence of protein and/or cellular casts. Fractional Excretion of Sodium (FENa). Can help differentiate be- tween the three types of acute renal injury: prerenal, intrinsic, and postrenal. FENa 5 (PCr 3 UNa) / (PNa 3 UCr). FENa ,1% suggests prerenal causes,.1% suggests intrinsic causes,.4% suggests postrenal causes (i.e., bilateral ureteral obstruction). Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 620 CHAPTER 24 Principles and Acute Management Assessment of Renal Function. Measurement of GFR is consid- ered the gold standard, though is commonly estimated using se- rum creatinine levels. Creatinine is a waste product of muscle metabolism and can be influenced by age, muscle mass, and gen- der. In general, a GFR.90 mL/min/1.73 m2 is considered normal, between 60 and 90 mL/min/1.73 m2 is considered a mild decline in renal function, between 30 and 60 mL/min/1.73 m2 is a moder- ate decline in renal function, between 15 and 30 mL/min/1.73 m2 is a severe decline in renal function, and ,15 mL/min/1.73 m2 is considered renal failure. IMAGING STUDIES (Tables 24.1 and 24.2) Renal ultrasonography is considered a first-line modality in the evaluation of suspected upper urinary tract obstruction. Advan- tages include low cost, widespread availability, and lack of ionizing radiation. The information obtained by ultrasound is primarily anatomic and can provide renal size, cortical thickness, corticome- dullary differentiation, and the grade of collecting system dilation (hydronephrosis). Although the presence of hydronephrosis is suggestive of underlying obstruction, it is important to recog- nize that hydronephrosis is an anatomic finding, not a functional diagnosis, and that hydronephrosis alone does not indicate urinary tract obstruction. The main downside of renal ultraso- nography is that it is often unable to visualize the etiology of a potential obstruction, which often is located in the ureter, an area more challenging to confidently image via ultrasonography alone. Duplex Doppler sonography, which allows for identification of arterial waveforms, has been postulated as a tool to help detect Table 24.1 M  edian Reported Sensitivity and Specificity for Diagnosis of Ureteral Calculi Relative to Noncontrast MEDIAN MEDIAN MODALITY SENSITIVITY (%) SPECIFICITY (%) Conventional radiography 57 76 Ultrasound 61 97 Intravenous pyelography 70 95 MRI 82 98.3 CT (not as gold standard) 98 97 CT, Computed tomography; MRI, magnetic resonance imaging. (Adapted from Fulgham PF, Assimos DG, Pearle MS, Preminger GM. Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment, 2012). Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 621 urinary obstruction via calculation of a resistive index (peak sys- tolic velocity-end diastolic velocity/peak systolic velocity). In gen- eral, a resistive index of 0.70 is considered to be the upper limits of normal in adults; however, a wide variety of factors have been found to influence this measurement, limiting its widespread ap- plicability. Color Doppler ultrasonography has also demon- strated utility in distinguishing obstructive from nonobstructive causes of obstruction by helping identify the presence of a ureteral jet in the bladder. Computed Tomography (CT) Cross-sectional imaging with a CT scan is considered the standard in the evaluation of urinary stone disease. CT has the advantage of speed, safety, and accuracy with reported Table 24.2 E stimated Effective Radiation Dose by Type of Imaging Examinationa EFFECTIVE TYPE OF EXAM DOSE (MSV) Ultrasound (US) Abdomen and pelvis US 0 Magnetic resonance Abdomen and pelvis MRI 0 imaging (MRI) Conventional radiography KUB 0.7 KUB with tomograms 3.9 IVU 3.0 Computed tomography (CT) Noncontrast CT, abdomen and pel- 10.0 vis Without and with contrast CT, 15.0 abdomen and pelvis (two-phase) Without and with contrast CT, 20.0 abdomen and pelvis (three-phase) Noncontrast CT, abdomen and 3.0 pelvis (low-dose protocol) Ultra-low dose protocol CT ,1.9 a Rob S, Bryant T, Wilson I, Somani BK. Ultra-low-dose, low-dose, and standard-dose CT of the kidney, ureters, and bladder: Is there a difference? Results from a systematic review of the literature. Clin Radiol 2017;72:11-15. Crossref, Medline, Google Scholar. Adapted from Fulgham PF, Assimos DG, Pearle MS, Preminger GM. Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment, 2012. Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 622 CHAPTER 24 Principles and Acute Management sensitivity rates of 96% for stone detection and specificity and positive predictive values of 100%. CT can detect most urinary stones with rare exceptions (i.e., protease inhibitor stones). It has also demonstrated the ability to identify a wide spectrum of alternative diagnoses, around 10% in patients being evaluated for renal colic. When a stone is not identified as being a source of upper urinary tract obstruction, CT urography (CTU) may be considered. Conventional CTU involves three phases: an unenhanced noncontrast phase, a nephrogenic phase at 100–120 seconds after contrast administration, and an excretory phase obtained several minutes afterward after the kidneys have had an opportunity to drain. The primary drawback of CT scanning is radiation exposure. Low-dose and ultra-low dose radiation protocols may be used with similar performance capabilities, especially in the case of stones and when the body mass index (BMI) is low (Fig. 24.3). Magnetic Resonance Urography (MRU) MRU is the best cross-sectional alternative to a CT scan because it is also able to provide excellent anatomic information without ionizing radiation. The main drawbacks of this diagnostic mo- dality are that it is more costly and more restricted and does not directly identify most urinary stones. MRU can provide some unique functional information related to obstruction because the administration and uptake of contrast have been shown to cor- relate well with differential renal function, but contrast excretion has been shown to correlate well with renal scintigraphy (mea- sured as renal transit time). One concern when considering MRU is the potential for nephrogenic systemic fibrosis (NSF), which has been linked to gadolinium-based agents and can occur in patients with severe renal impairment. Group II agents are not contraindicated. Nuclear Renography Nuclear medicine renography is the only imaging modality that can provide noninvasive information about dynamic renal function. The most commonly performed nuclear medicine scan for this purpose is technetium-99m-mercaptoacetyltriglycine (99mTc-MAG3) because it has high excretion by the kidneys, rapid clearance, low radiation dose, and tubular secretion. It is Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  Exceptions: Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. Abdominal, flank, Known radiopaque stone former Contrast allergy or back pain Renal insufficiency Pregnancy (ACOG) Pediatric patients Noncontrast CT of the abdomen and pelvis No Yes Noncontrast CT of the abdomen and pelvis BMI ≤30 or KUBa standard protocol or KUBa low-dose protocolb Ureteral Yes Yes Ureteral CHAPTER 24 Principles and Acute Management 623 calculus calculus Report: No Stone size No Stone location Stone Attenuation Further workup for Further workup for Skin to stone distance etiology of symptoms etiology of symptoms Hydronephrosis as indicated as indicated Congenital anomalies Extravasation Stranding Management per AUA guidelines Definitive interventional Observation and medical a KUB is obtained if stone is not seen on CT scout film. management management b Low-dose protocol not recommended for patients with BMI >30. FIG. 24.3 Algorithm for diagnosis and management of suspected ureteral obstruction from a stone. ACOG, American College of Obstetricians and Gynecologists; AUA, American Urological Association; BMI, body mass index; CT, computed tomography; KUB, kidney, ureter, and bladder. (Adapted from Fulgham PF, Assimos DG, Pearle MS, Preminger GM. Clinical effectiveness protocols for imaging in the management of ureteral cal- culous disease: AUA technology assessment, 2012.) 624 CHAPTER 24 Principles and Acute Management preferred over technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) because it has a higher renal uptake. Renal obstruction is most commonly determined based on the T1/2 (time for one half of the tracer to leave the collecting system). By convention, if the T1/2 is ,10 minutes, the kidney is considered unobstructed. If the T1/2 is.20 minutes, the kidney is consid- ered obstructed, and if the T1/2 is between 10 and 20 minutes, the results are considered equivocal. One possible false positive to watch for is the potential for prolonged washout times in the setting of massive collecting system dilation or poor renal func- tion. This can be minimized with the administration of a diuretic during the study (furosemide) to accelerate urine flow. Various protocols exist, and it is important to take this into consideration when interpreting results and particularly comparing them to prior studies, which may have been performed with different protocols. Excretory Urography Before the advent and widespread availability of CT scans, excretory urography (intravenous pyelography) was the imaging modality of choice to diagnose upper urinary tract obstruction. Some of the downsides of this approach include the lack of detailed anatomic imaging of structures around the kidney and ureters as well as the fact that the test itself is dependent on GFR. Further, it requires instillation of contrast, which may not be feasible in patients with renal insufficiency or contrast aller- gies or in those whom radiation exposure is a concern (i.e., pregnancy). Whitaker Test The primary rationale for performing a Whitaker test is to differentiate obstructive from nonobstructive hydronephrosis. This test requires a percutaneous needle or nephrostomy in the collecting system through which contrast is infused at 10 mL/ min. Intrapelvic pressures are monitored, as are intravesical pressures, which are obtained from a urodynamic catheter placed in the bladder. Measurements are taken by subtracting the intravesical pressures from the intrapelvic pressures as urine passes the ureteropelvic junction (UPJ) and then ureterovesical junction (UVJ). Pressures ,15 cm H2O are considered normal, Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 625.22 cm H2O is indicative of obstruction, and between 15 and 22 cm H2O is considered indeterminate. ACUTE MANAGEMENT Two of the critical decisions upon the identification of upper urinary tract obstruction are symptom control and the need for drainage. In the event of symptomatic obstruction, characterized by renal colic, there is a need for analgesia. Non-narcotic treat- ment should be first-line therapy. Nonsteroidal antiinflammatory drugs (NSAIDs) can be very effective. They work by decreasing renal blood flow and subsequently renal pelvic pressure, which can lead to pain relief. They have been clinically shown to be superior to opioids with a greater decrease in pain scores, lesser instance of gastrointestinal side effects, and decreased need for second-line analgesia. It is important to be aware of the patient’s renal function prior to NSAID administration because the reduction of renal blood flow can be detrimental, particularly in the setting of acute or chronic renal insufficiency. Other treat- ments for renal colic include acetaminophen, alpha blockers, cortico-steroids, and opioids. Additionally, antiemetics can be used in the event of concomitant nausea or vomiting, which oc- curs quite frequently in the setting of ureteral obstruction. The second consideration that should be made in each case of obstruction is an assessment as to whether or not acute drainage is indicated. Typically, drainage can be achieved either by retrograde ureteral stenting, antegrade nephrostomy tube placement or by relieving the primary source of obstruction (such as in the case of a ureteral stone). The decision of whether acute drainage is warranted should be based on several factors. Acute drainage or decompression of an obstructed upper urinary tract should occur promptly in the setting of infection and has shown the potential to be lifesaving therapy in the event of severe infection or sepsis. In such instances, it is advisable to achieve drainage alone and tempo- rize the obstruction because excess manipulation of the infected, obstructed urinary tract could exacerbate the underlying illness. Another scenario in which prompt drainage should be performed is in the event of bilateral renal obstruction or obstruction of a solitary kidney because there is a greater potential risk of renal in- jury without a contralateral functioning kidney to compensate. Similarly, prompt drainage should be considered whenever any Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 626 CHAPTER 24 Principles and Acute Management degree of obstruction (with high intrarenal pressures) is suspected in the setting of infected urine, immunocompromised patients or risk for renal failure. Methods of Upper Urinary Tract Drainage Retrograde Ureteral Stent Placement. Retrograde ureteral stent placement is typically preferred for most cases of ureteral obstruc- tion. Advantages of retrograde ureteral stent placement include the utilization of existing anatomy and orifices, a completely inter- nal drainage without the need of any external drains or appliances, and in most cases a high degree of success that can be achieved with minimal sedation. Additionally, retrograde stenting can be performed on patients at high risk of bleeding. Disadvantages of retrograde stenting include the need to use cystoscopy and iden- tify the ureteral orifice in order to place the stent and achieve renal decompression. Certain scenarios may make this challenging such as reconstructed lower urinary tract anatomy (ileal conduits, neobladders, transplant) or the presence of lower extremity con- tractures or anatomy precluding the ability to be placed in lithot- omy. Other scenarios in which a retrograde ureteral stent may not be effective is in the event of severe obstruction such as with a densely impacted stone or stenosis whereby the passage to the kidney is completely obscured. Similarly, high-grade extrinsic compression as may be seen in the case of advanced malignancy or iatrogenic injury with a suture or clip may make retrograde passage impossible. Technique. Prior to placement of a ureteral stent, AUA guidelines may recommend antibiotic prophylaxis (see Chapter 3). The proce- dure can be performed under local anesthesia, but sedation or gen- eral anesthesia is generally preferable. The procedure begins with placement of a cystoscope into the bladder. When in the bladder, a guidewire is used to cannulate the ureteral orifice of the affected kidney and attempt passage to the renal collecting system. Various guidewires exist and differ in their degree of stiffness and coatings. Typically, less stiff hydrophilic wires are safer with a decreased risk of inadvertent ureteral perforation and may be better suited to bypass obstruction. Conversely, stiffer wires allow for more secure retro- grade access and can make it easier to pass a stent. Wires can be ex- changed through open-ended catheters. Hybrid wires (PTFE coated Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 627 A B C FIG. 24.4 (A) Cystoscope in bladder plus guidewire in ureter. (B) Stent placed in ureter through 10-Fr sheath (asterisk indicates radiopaque marker of pusher; arrow indicates 10-Fr sheath). (C) Guidewire and 10-Fr sheath removed; distal stent section coiled in bladder. nitinol shaft with hydrophilic tip) offer the benefits of both of these features. When the wire is in the kidney, the open-ended catheter can be passed over it to perform retrograde pyelography with gentle in- stillation of contrast medium. This can be useful in detailing the renal collecting system anatomy and characterizing the degree of obstruc- tion. It is also advisable to obtain a urine culture from the kidney at this time, especially in cases of suspected infection. The working wire should then be replaced and the stent placed coaxially until there is a curl in the kidney as well as in the bladder to ensure it stays in position (Fig. 24.4). Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 628 CHAPTER 24 Principles and Acute Management A B FIG. 24.5 Different stent designs. (A) Polaris Loop stent, Polaris Ultra stent, Percuflex Plus stent, and Contour VL stent. (B) Resonance metal stent. (A, Courtesy of Boston Scientific, Marlborough, MA; B, Courtesy of Cook Medical, Bloomington, IN.) Ureteral Stents. Most stents are made of flexible polymers such as polyurethane or silicone. Metallic stents are available for use in instances of severe external compression and have been shown to be more resistant to obstruction. Although most stents have a double-J configuration, other designs exist as well, including single-J stents with only a proximal curl and other novel distal ends in an effort to decrease stent related lower urinary tract symptoms (Fig. 24.5). Ureteral stent symptoms are common and typically include flank discomfort, especially with voiding, bladder pain, hematuria, and dysuria, as well as urinary frequency and urgency. There is a validated ureteral stent symptom questionnaire designed to help characterize stent symptoms and identify meaningful ways to minimize them. To date, there are varying opinions on whether stent length and position are associated with worsened symptoms; however, alpha blockers and antimuscarinics have been shown to improve stent tolerability. Antegrade Nephrostomy Tube Placement. Percutaneous nephros- tomy tube insertion into the kidney is the other primary method of achieving upper tract drainage (Fig. 24.6). Advantages of this approach are the fact that it is potentially more definitive by ad- dressing the kidney directly and can be achieved most rapidly and most definitively. One of the disadvantages to percutaneous neph- rostomy tube insertion is the fact that it is more invasive and re- quires placement of a needle and tube directly through the renal Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 629 FIG. 24.6 Cope catheter with the retention string loosened for demonstration. parenchyma. As a result there is higher potential for bleeding, and as such, this approach is contraindicated in patients with untreated coagulopathy. The decision on whether or not to place a retrograde stent or antegrade nephrostomy tube depends on the indication, the pa- tient’s medical condition and anatomy, and preferences of both the patient and physician. Both approaches have been found to be effective in their potential to resolve fevers in patients with obstruction and infection. Another important consideration is patient quality of life in which temporary nephrostomy tubes have been found to have an improvement in health-related quality of life. Technique. A majority of percutaneous nephrostomy tubes are placed by interventional radiologists, although communica- tion between the urologist and interventional radiologist is im- portant, especially in cases in which percutaneous tube place- ment may ultimately be used at a later date for an antegrade procedure such as percutaneous nephrolithotomy. Antimicrobial prophylaxis should be administered prior to the procedure, and all anticoagulation should be held. Local or general anesthesia may be used. Patients may be positioned in either the prone or supine position. The prone position (Fig. 24.7) offers the advantage of optimizing Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 630 CHAPTER 24 Principles and Acute Management Endotracheal tube to anesthesia machine (head on side) Arm rest Foam bolster for chest Foam donuts for knees Foam bolsters for ankles Foot padding FIG. 24.7 Padding for prone positioning. Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 631 Posterior calyces Posterior Brödel line of incision Frontal 20° plane 70° Brödel white line and imaginary wedge of Bertin Anterior Anterior calyces A Posterior 70° 20° B Anterior FIG. 24.8 Relation of anterior and posterior calyces to renal parenchyma in Brödel-type kidney (A) and Hodson-type kidney (B). The optimal site of percuta- neous entry from the posterior aspect of the kidney is into a posterior calyx be- cause the path into the renal pelvis is fairly straight. If entry is into an anterior calyx (from the posterior aspect of the kidney), then an acute angulation must be made to enter the renal pelvis, which may not be possible with rigid instru- mentation. (From Smith AD. Controversies in endourology. Philadelphia: Saunders, 1995.) potential sites of puncture into the kidney, particularly along the posterior calyces (Fig. 24.8). The upper pole in particular is favorable in the prone position owing to the posterior orientation of the upper pole in general (Fig. 24.9). Another advantage of the prone position is that it affords the operator access to both kidneys as may be war- ranted in the event of bilateral obstruction. One of the disadvantages Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 632 CHAPTER 24 Principles and Acute Management FIG. 24.9 Retrograde pyelogram with air and contrast shows air in upper pole compound calyx and posterior lower pole calyx. of the prone position is the potential for decreased cardiac index and higher peak inspiratory pressures, though there is conflicting evi- dence to support this (Fig. 24.3). When placing patients in the supine position, typically the patient is positioned with the ipsilateral side toward the most lateral aspect of the table and the flank elevated with a bolster or 3-L bag of saline underneath the lumbar fossa. One ad- vantage is the potential to more easily work from a retrograde posi- tion simultaneously in the absence of the availability of split leg table adaptors which allows for simultaneous antegrade/retrograde access in the prone position. Disadvantages include a lesser surface are for renal puncture and potential difficulty reaching the upper pole. Access may be guided either via fluoroscopy or ultrasound. One advantage to fluoroscopy is that the full renal anatomy can be visualized at once. Further, access needles and tubes that are radi- opaque can be confidently visualized, and there is potential to see stones, which are a common source of obstruction (Fig. 24.10). Disadvantages include exposure to the patient, surgeon, and Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.  CHAPTER 24 Principles and Acute Management 633 A B FIG. 24.10 Triangulation fluoroscopic guidance. (A) With the top of the fluo- roscopy unit rotated laterally and cephalad, adjust the access needle (arrows) to a mediolateral orientation of the needle. (B) After rotating the top of the fluoroscopy unit medially and while keeping mediolateral orientation of the needle constant, move the needle in the cephalo-caudad plane until the needle is again aimed toward the desired calyx. (From Miller NL, Matlaga BR, Lingeman JE. Techniques for fluoroscopic percutaneous renal access. J Urol 2007;178:15-23.) Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved. 634 CHAPTER 24 Principles and Acute Management operating room personnel to radiation as well as a lack of three- dimensional imagery, which can make it challenging to interpret the position of the needle relative to the kidney and desired point of access. One of the main limitations is also the need for opacifi- cation of the collecting system. In some cases, this can be achieved via retrograde instillation of contrast through an open-ended cath- eter. Alternatively, a combined approach is commonly utilized whereby ultrasound is used to advance a needle into the kidney to achieve access and then contrast is instilled for the purpose of us- ing fluoroscopy to guide the ultimate nephrostomy tube into a se- lected calyx. Ultrasound-guided access offers decreased radiation and lesser cost. It is additionally advantageous in providing a bet- ter three-dimensional perspective and can also identify surround- ing viscera such as lung, pleura, spleen, liver, and bowel. Further, no opacification of the renal collecting system is necessary. One of the disadvantages of ultrasound is that it can be challenging to gain a confident image of the kidney, especially in obese patients with high BMIs. Suggested Readings Assimos D, Krambeck A, Miller NL, et al. Surgical Management of kidney stones, AUA/ Endourology Society Guideline. 2016. Fulgham PF, Assimos DG, Pearle MS, Preminger GM. Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment. 2012. Nord RG, Cubler-Goodman A, Bagley DH. Prone split-leg position for simultaneous retrograde ureteroscopic and percutaneous nephroscopic procedures. J Endourol 1991;5(1):13-16. http://doi.org/10.1089/end.1991.5.13. Downloaded for ahmed eliwa ([email protected]) at Egyptian Knowledge Bank from ClinicalKey.com by Elsevier on November 14, 2022. For personal use only. No other uses without permission. Copyright ©2022. Elsevier Inc. All rights reserved.