Diagnostic Considerations
The differential diagnoses of flank pain or hematuria include a plethora of conditions with infectious, neoplastic, congenital, metabolic, and hematogenous sources. Intraluminal and extraluminal lesions may result in ureteral obstruction.
If acute ureteral obstruction manifests as hematuria, colic, and flank pain, consider that nephrogenic calculi may have embolized to the ureter. Approximately 15% of all calculi, particularly uric acid stones, are not radiopaque (ie, visible on plain radiographs); therefore, the examining clinician needs to perform further imaging studies for an accurate identification.
Computed tomography (CT) scanning is an excellent imaging modality for identifying all calculi (including uric acid stones), [20] except for the rare indinavir crystal concretions that form in the ureters of patients with HIV infection who are taking this protease inhibitor. If calculi are not seen on a CT scan, consider the possibility of an obstructing urothelial tumor; cytology and endoscopic procedures help to determine this diagnosis.
Blood coagulum downstream from a bleeding source in the kidney (eg, renal cell carcinoma, angioma, angiomyolipoma, arteriovenous malformation, trauma to a pyelonephritic or multicystic kidney) can also manifest with a similar clinical picture. If a patient has acute ureteral obstruction with fever and leukocytosis, suggesting pyonephrosis, the preferred treatment is resuscitation, drainage, and intravenous antibiotics. Further diagnostic studies can be performed later, once the physician is certain that the system is sterile. This strategy prevents further clinical deterioration.
Extraureteric causes of ureteral obstruction include retroperitoneal lymphadenopathy from metastatic tumors or lymphoma, retroperitoneal fibrosis, uterine myoma, bladder masses, and high-stage pelvic tumors (eg, cervical cancer).
Anything that causes severe bladder outlet obstruction leads to bilateral hydronephrosis or hydronephrosis of a solitary kidney. Congenital anomalies can also directly obstruct or provide stasis that may lead to pyelonephritis and papillary necrosis. Duplicate collecting systems, vesicoureteral reflux, and ureteroceles are important offenders to consider.
In the clinical scenario of fever, chills, prostration, and sepsis without hydronephrosis, the differential diagnoses include pyelonephritis, perinephric abscess, renal hemorrhage, tubulointerstitial nephritis, and glomerulonephritis.
In otherwise asymptomatic patients who present with acute kidney injury characterized by azotemia, the physician must consider bilateral obstruction or the presence of a solitary obstructed kidney. Renal ultrasonography is a wise first test in this scenario, along with tests for urine and plasma urea, creatinine, sodium, and osmolality. After excluding postrenal causes, consider prerenal and renal sources.
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In this figure, the multifactorial nature of renal papillary necrosis is represented by 5 of the disease's most frequently associated conditions: infection, obstruction, diabetes mellitus, analgesic abuse, and sickle cell disease. Each circle represents a condition. Note how the conditions overlap; the red areas show the coexistence of 2 conditions, and the black areas represent 3 coexistent conditions. Multiple conditions exhibit synergism and, therefore, worsen both the severity of the disease and the prognosis.
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Cystoscopic photograph of sloughed papilla extruding from the ureteral orifice. The patient was a 51-year-old man with poorly controlled diabetes and a history of microhematuria and an acute onset of severe left flank pain. Findings of upper tract imaging with a renal ultrasonography and intravenous pyelography were remarkable only for mixed heterogeneity consistent with medical renal disease. Urine cytology results were negative, and culture showed no growth. In-office flexible cystoscopy revealed the mass extruding from the left ureteral orifice, which required sedation and rigid cystoscopy to extract. Gross examination yielded a tan, friable, irregular, wedge-shaped soft tissue mass 1.7 cm X 1.6 cm X 1.5 cm. Bilateral retrograde pyelography revealed a clubbed left upper pole calyx and no other filling defects. The pathology was necrotic epithelial tissue.
