What is the appropriate evaluation and management for an adult patient with left abdominal pain radiating to the back, leukocytosis (elevated white blood cell count), and microhematuria (presence of blood in the urine)?

Evaluation and Management of Left Abdominal Pain with Leukocytosis and Microhematuria

This clinical triad strongly suggests either acute pyelonephritis with possible perinephric extension or complicated urolithiasis, and requires urgent CT urography with IV contrast to identify the source and guide management. 1, 2

Immediate Diagnostic Approach

The combination of left-sided abdominal pain radiating to the back, leukocytosis, and microhematuria creates a high-risk scenario requiring urgent imaging evaluation. CT urography (multiphasic) is the preferred imaging modality because it can simultaneously evaluate for:

• Urolithiasis (kidney or ureteral stones causing obstruction) 1, 2
• Pyelonephritis with or without perinephric abscess 1, 2
• Renal cell carcinoma or other renal masses 1, 2
• Transitional cell carcinoma of the upper urinary tract 1, 2

The ACR Appropriateness Criteria establish CT urography as having 96% sensitivity and 99% specificity for detecting upper tract urologic pathology, making it superior to all other imaging modalities for this presentation. 1

Critical Laboratory Evaluation

Before imaging, obtain:

• Complete urinalysis with microscopy to confirm ≥3 RBCs/HPF and assess for pyuria, bacteria, and casts 2, 3
• Urine culture (preferably before antibiotics if infection suspected) 2, 3
• Serum creatinine and BUN to assess renal function 2, 3
• Complete blood count to quantify leukocytosis and assess for anemia 2, 3

Differential Diagnosis Priority

Most Likely Urologic Causes (Given Pain Radiation to Back)

Acute pyelonephritis is highly probable when left flank/abdominal pain, fever, and leukocytosis occur together, particularly with microhematuria. 2, 3 The pain radiation to the back is characteristic of renal or ureteral pathology rather than colonic disease. 1, 2

Obstructive urolithiasis with secondary infection represents a urologic emergency requiring urgent decompression if confirmed. 1, 2 Kidney stones cause painful hematuria with characteristic flank-to-groin radiation. 2, 3

Renal abscess or perinephric abscess must be excluded, as these require drainage in addition to antibiotics. 2, 3

Less Likely but Important Considerations

Diverticulitis typically presents with the triad of left lower quadrant pain, fever, and leukocytosis, but microhematuria is uncommon and pain radiation to the back is atypical. 1 The ACR guidelines note that CT with IV contrast is the preferred test for suspected diverticulitis, achieving high sensitivity for detecting complications. 1

Renal malignancy (renal cell carcinoma or transitional cell carcinoma) must be considered in any adult with hematuria, though acute presentation with leukocytosis is less typical. 1, 2, 3

Imaging Protocol Specifics

Multiphasic CT urography should include:

• Unenhanced phase (to detect stones and baseline attenuation) 1, 2
• Nephrographic phase (optimal for renal parenchymal evaluation) 1, 2
• Excretory phase (to evaluate collecting systems, ureters, and bladder) 1, 2

This protocol has 99.6% accuracy for detecting upper tract lesions compared to 84.9% for traditional intravenous urography. 1

Management Algorithm Based on Imaging Results

If Obstructive Urolithiasis with Infection Confirmed:

• Urgent urologic consultation for possible decompression (nephrostomy tube or ureteral stent) 2, 3
• Broad-spectrum IV antibiotics after obtaining cultures 2, 3
• This represents a urologic emergency with high morbidity if untreated 2, 3

If Pyelonephritis Without Obstruction:

• IV antibiotics targeting gram-negative organisms 2, 3
• Repeat imaging if no clinical improvement within 48-72 hours 2, 3
• Consider abscess formation if persistent fever despite appropriate antibiotics 2, 3

If Renal Mass Identified:

• Urologic referral for further characterization and management 2, 3
• Even if infection is present, malignancy evaluation cannot be deferred 2, 3

If Diverticulitis Confirmed:

• Severity staging guides management (mild cases: oral antibiotics; complicated cases: IV antibiotics ± intervention) 1
• CT identifies complications requiring surgical consultation (perforation, abscess >4cm, fistula) 1

Critical Pitfalls to Avoid

Never attribute hematuria solely to infection without imaging in adults. The combination of hematuria with systemic symptoms requires exclusion of obstructive uropathy and malignancy. 2, 3 Antibiotic therapy alone without imaging risks missing life-threatening conditions like obstructed infected kidney or underlying malignancy. 2, 3

Do not rely on ultrasound as the sole imaging modality in this presentation. While ultrasound may detect hydronephrosis, it has poor sensitivity for ureteral stones (only 38% for ureteral calculi) and cannot adequately evaluate for pyelonephritis complications or upper tract malignancy. 1, 2

Pain radiation to the back strongly suggests urologic rather than colonic pathology. While diverticulitis can cause left lower quadrant pain with leukocytosis, the back radiation and microhematuria make renal/ureteral pathology more likely. 1, 2

Follow-Up Considerations

If initial CT urography is negative but hematuria persists:

• Cystoscopy is mandatory to evaluate the bladder for transitional cell carcinoma 2, 3
• Repeat urinalysis at 6,12,24, and 36 months with blood pressure monitoring 2, 3
• Consider nephrology referral if proteinuria, dysmorphic RBCs, or declining renal function develops 2, 3

Gross hematuria developing at any point requires immediate re-evaluation given the 30-40% malignancy risk. 2, 3