PE20.8-9 | Urine and KUB Interpretation — Summary & Reflection

KEY TAKEAWAYS

Urine Examination and KUB Interpretation — key takehome points:

Urinalysis (PE20.8):
• Collection method matters: bag urine = high contamination; SPA/catheter = gold standard in infants; clean-catch MSSU in older children.
• Dipstick blood positive + no RBCs on microscopy = myoglobinuria (rhabdomyolysis) not haematuria.
• RBC casts = pathognomonic of glomerulonephritis — present ONLY when RBCs enter the tubule through a damaged glomerular barrier; absent in UTI/calculus/trauma.
• Cast types: hyaline (benign) → granular (ATN/CKD) → waxy (advanced CKD) → RBC (GN) → WBC (pyelonephritis/AIN).
• Isosthenuria (fixed SG 1.010) = loss of tubular concentrating and diluting ability = advanced CKD marker.
• Glucosuria without hyperglycaemia = proximal tubular dysfunction (Fanconi syndrome).

KUB X-ray (PE20.9):
• Radio-opaque calculi: calcium oxalate/phosphate (most common), struvite (staghorn), cystine (faint). Uric acid = radiolucent — NOT visible on plain film.
• Adrenal calcification on KUB in a child with abdominal mass = neuroblastoma pattern (~85% calcify).
• Wilms tumor: rarely calcifies; renal origin; does not cross midline.
• Systematic KUB reading: adequacy → bones → calcification (renal/ureteric/bladder/suprarenal) → soft tissue outlines → bowel/gas.

REFLECT

Reflect on the hook scenario: the urinalysis showing RBC casts, and the KUB with adrenal calcification. How many different clinical syndromes did these two investigations distinguish in the clinical integration section? Consider: how does developing a systematic approach to each investigation — rather than pattern-matching to the obvious abnormality — protect against missing coexistent or less obvious findings? In your clinical postings, make a habit of reviewing every urinalysis and every KUB systematically and documenting your interpretation in the notes — this is how interpretive skills become automatic rather than effortful.