Papillary Necrosis Workup

Updated: Jan 12, 2017
  • Author: Christopher Powell, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Workup

Laboratory Studies

See the list below:

  • The general diagnostic studies include a urinalysis (ie, routine, microscopic), a complete blood cell count, a complete metabolic panel, and prothrombin time and activated partial thromboplastin time determinations. If patients have concomitant fever, obtain urine and blood cultures under sterile conditions. If patients are prostrate and obtunded, measure arterial blood gases and perform standard electrocardiography and chest radiography. If acute obstruction is suspected, perform renal ultrasonography or another radiographic evaluation and request an immediate consultation with a urologist.
  • Patients who present with hematuria, even if diagnostic interventions indicate papillary necrosis, require a full urologic workup for their hematuria because they may have a concomitant bladder tumor or similar lesion.
    • Perform a routine and microscopic urinalysis from properly collected specimens (ie, sterile catheterization, clean-catch midstream).
    • Perform a urine culture obtained via sterile catheterization or clean-catch midstream.
    • Obtain a urine cytology study on a voided specimen.
    • Perform an imaging study, preferably with intravenous contrast, to evaluate the upper urinary tract. Use CT scanning or intravenous urography (IVU), depending on preference. Perform the imaging study prior to cystoscopy because if the study is limited or incomplete, a urologist may need to perform bilateral retrograde pyelography (RPG) in addition to routine cystoscopy. The test of choice to evaluate the upper tracts of patients with contraindications to intravenous contrast is a bilateral RPG.
    • If necessary, perform a cystoscopy (ie, flexible or rigid) with bilateral RPGs.
    • Ureteroscopy may be indicated if the RPG reveals a filling defect in either collecting system. Do not dismiss any persistent collecting system filling defect as a sloughed papilla or blood clot until certain it is not a urothelial papillary tumor or radiolucent stone.
  • The most common urinalysis findings include proteinuria, pyuria, bacteriuria, and low urine-specific gravity. More than 50% of patients develop leukocytosis and azotemia.
  • An acutely elevated serum creatinine may be the result of either a bilateral or unilateral process. This process can be obstructive or may be the manifestation of some toxic, metabolic, or inflammatory insult.
  • Patients with known or possible obstruction require an urgent consultation with a urologist.
  • If the clinical picture is suggestive, investigate for any of the conditions associated with renal papillary necrosis, including pyelonephritis, obstructed urinary tract, hemoglobinopathies, tuberculosis, liver cirrhosis, analgesic abuse, renal transplant rejection, and diabetes mellitus.
  • Clinical findings may also prompt performing hemoglobin electrophoresis, a subdermal tuberculin test, liver function tests, serum ammonium measurements, serum and urine salicylate and acetaminophen levels, a hemoglobin A1c measurement, and cyclosporin or tacrolimus levels.
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Imaging Studies

For representative images, refer to Papillary Necrosis in the Radiology section.

  • Plain radiography
    • Standard radiography of the abdomen that visualizes the span of the kidneys, ureters, and bladder is very good for visualizing radiopaque calculi and may offer hints as to whether the patient has 2 kidneys. However, this imaging modality neither yields information on the integrity of the urinary tract nor helps to diagnose hydronephrosis or to elucidate kidney function.
    • Thus, plain radiography is not paramount because it is generally not diagnostic for renal papillary necrosis. Much better radiographic tools are available for this purpose.
  • CT scanning
    • If the clinical scenario suggests acute obstruction, CT scanning is the imaging modality of choice, mostly because it is extremely accurate for diagnosing calculi—one of the prime differential diagnoses of a sloughed papilla.
    • A CT scan also shows the entire anatomy of the collecting system and easily reveals hydronephrosis, inflammatory changes, and purulent collections, all without the administration of intravenous contrast. With the administration of contrast and delayed films, if necessary, clinicians can easily visualize filling defects. Contrast images also provide a good, albeit unquantified, estimate of cortical function.
    • CT scans can also be used to accurately diagnose renal papillary necrosis. Historically, subsequent verification via IVU was required. However, Lang et al have shown that they can identify papillary and medullary necrosis at an early and reversible stage using multiphasic helical CT scanning. [14, 15] When adequately treated with antibiotics, reperfusion improved in approximately 60% of patients within 3 months.
    • When intravenous contrast is contraindicated, CT scanning without contrast may be ideal for diagnosing acute obstruction, estimating renal function, and, most importantly, excluding nephrolithiasis or ureterolithiasis. Ultrasonography has similar capabilities but, without high-grade obstruction, is not as sensitive for diagnosing calculi. Although less expensive and less invasive (ie, no radiation exposure), ultrasonography is operator-dependent and less sensitive for diagnosing calculi. A bilateral RPG is preferred in patients with contraindications to intravenous contrast and in those in whom the urinary tract must indispensably be opacified.
    • CT findings include (1) small kidneys, (2) ring shadows in the medullae, (3) contrast-filled clefts in the renal parenchyma, and (4) renal pelvic filling defects.
    • Lang et al describe the ischemic changes of early medullary and papillary necrosis as "a circumscribed, yet often poorly marginated area of diminished enhancement in the tip of the medullary period." They claim these changes can be seen on scans taken in the early corticomedullary phase but are best seen on scans taken in the nephrographic phase. [14, 15]
  • Intravenous urography with nephrotomography
    • This modality provides an excellent display of the anatomy; even very minor morphological changes in the urinary tract are precisely documented.
    • IVU is typically the imaging method of choice for diagnosing renal papillary necrosis, although it has its limitations. Clear IVU imaging largely depends on a paucity of stool or bowel gas, which is usually not the case, meaning that images can be obscured. Additionally, approximately 15% of calculi are not radiopaque; thus, IVU is not the best initial test in patients who present with colic, in whom stones are more common and who require a different workup and treatment plan. In addition, in severe cases, renal function may be so poor that diagnostic changes cannot be demonstrated. Lastly, IVU is contraindicated in patients with azotemia and in patients with coexisting diseases, particularly allergy, asthma, dehydration, diabetes mellitus, thyrotoxicosis, and plasmocytoma. With the advances in CT imaging and the limitations of IVU, many clinicians and radiologists consider CT scan the imaging modality of choice for renal papillary necrosis.
    • If, for any reason, IVU is not the best choice, contrast-enhanced CT scanning, with its far superior contrast resolution, may demonstrate necrotic detached papillae within medullary cavities, thus establishing the diagnosis.
    • IVU findings include (1) shrinkage and irregularity of papillae, with consequent widening of calyceal fornices, creating what are described as hooks and spurs; (2) desquamated papilla in situ, demarcated by contrast material as a ring shadow, often in a triangular shape (commonly referred to as the ring sign); (3) a calix without a papilla; (4) a partially calcified filling defect in the renal pelvis (ie, sequestered papilla); and (5) contrast-containing rice-grain–sized cavities in the papilla, which are pathognomonic for the medullary form of renal papillary necrosis.
  • Renal ultrasonography
    • This imaging modality is safe, quick, inexpensive, noninvasive, and diagnostic for hydronephrosis, certain anomalies, and stones large enough to provide a shadow. It is also operator-dependent, which should be taken into consideration.
    • Ulreich could not duplicate his IVU-confirmed diagnosis of renal papillary necrosis when reviewing the sonograms of the same patients. [16]
    • Vijayaraghavan et al describe sonographic features of necrotic sloughed papillae representing filling defects in the ureter. [17] In one third of their patients, necrosed papillae were visualized in cavities in the medullary region communicating with the calyces.
    • Ultrasonography findings may suggest the diagnosis late in the course of the disease but is not sensitive enough to be confirmatory in the earlier, more reversible phases of renal papillary necrosis.
  • Retrograde pyelography
    • This test is more invasive because it requires endoscopic access. Images may reveal a clubbed calyx or a filling defect in the ureter.
    • Precautions such as intravenous antibiotic prophylaxis must be taken because this procedure involves retrograde introduction of contrast, which can increase intrapelvic pressure and may lead to pyelovenous backflow of infectious material, thus predisposing the patient to sepsis. Gentle slow introduction of contrast decreases the likelihood of this complication, but intravenous antibiotics are warranted nonetheless.
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Diagnostic Procedures

Although CT scanning, IVU, and ultrasonography findings can suggest the diagnosis of renal papillary necrosis, urologic intervention confirms the diagnosis and excludes other obstructing agents (ie, tumors, stones, blood clots). See Surgical therapy.

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Histologic Findings

The characteristic pathologic finding is coagulative infarct necrosis. See Pathophysiology.

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