PA27.8-17 | Renal Pathology II: Tubulointerstitial, Vascular & Neoplastic — Graded Quiz

A 28-year-old bodybuilder collapses during an extreme exercise competition. He is brought to the emergency department with confusion, dark brown urine, and severe bilateral thigh and calf pain. Serum creatinine is 5.2 mg/dL (baseline normal). Urine dipstick is strongly positive for haem (3+) but microscopy shows fewer than 5 RBCs/hpf. Urine myoglobin is markedly elevated. Which pathological mechanism is primarily responsible for the acute tubular injury in this patient?

A 45-year-old woman is diagnosed with acute tubulointerstitial nephritis (ATIN) after a 2-week course of ampicillin for a urinary tract infection. She presents with fever, arthralgia, and a maculopapular rash. Urinalysis shows eosinophiluria, mild proteinuria, and white cell casts. Serum creatinine has risen from 0.8 to 3.2 mg/dL. Which immunological mechanism best explains the pathogenesis of ATIN in this drug-induced context, and why does withdrawal of the drug alone usually restore renal function?

A 34-year-old woman presents with right flank pain, fever (39.2°C), rigors, and dysuria for 4 days. Urine culture grows Escherichia coli (> 10^5 CFU/mL). A renal ultrasound shows swelling and increased echogenicity of the right kidney without obstruction. She has a history of recurrent cystitis. Urinalysis shows pyuria, bacteriuria, and white cell casts. Which pathological feature on renal biopsy best distinguishes acute pyelonephritis from glomerulonephritis or tubulointerstitial nephritis of other causes?

A 7-year-old girl develops haemolytic-uraemic syndrome (HUS) 5 days after a bloody diarrhoea illness confirmed as Shiga toxin-producing Escherichia coli O157:H7 infection. She has oliguria, haemoglobin 6.8 g/dL, platelet count 28 × 10^9/L, and a peripheral blood smear showing fragmented RBCs (schistocytes). Serum creatinine is markedly elevated. Which pathological mechanism best explains how Shiga toxin causes renal injury specifically in children?

A 52-year-old man undergoes nephrectomy for a 7 cm right renal mass discovered incidentally on CT. The cut surface shows a bright yellow-orange mass in the upper pole with areas of haemorrhage and necrosis. The tumour has a pseudocapsule but does not cross Gerota's fascia. Microscopically, large polyhedral cells with abundant clear cytoplasm are arranged in acini and tubules, with a delicate vascular network. Immunohistochemistry shows CK7 negative, CD10 positive, vimentin positive, and CA-IX positive. Loss of heterozygosity at chromosome 3p is confirmed. Which paraneoplastic syndrome is this patient at most risk for?

A 3-year-old boy presents with a large left-sided abdominal mass that does not cross the midline, discovered incidentally by his mother. CT scan reveals a 9 cm heterogeneous left renal mass with cystic and solid components. There is no calcification. Tumour biopsy shows triphasic morphology: blastemal cells (small blue cells with high N:C ratio), epithelial components (primitive tubules and glomeruloid structures), and stromal components (spindle cells in loose stroma). Which genetic event is most commonly associated with this tumour, and what is the clinical implication of bilateral disease in a child with WAGR syndrome?

A 58-year-old man with autosomal dominant polycystic kidney disease (ADPKD) is seen for routine follow-up. His creatinine is 3.8 mg/dL (eGFR 18 mL/min). Total kidney volume on MRI is 2,800 mL (normal < 250 mL). He is hypertensive, on four antihypertensive agents. He asks about tolvaptan, which his nephrologist is considering. Which pathogenetic mechanism of ADPKD cyst growth does tolvaptan specifically target?

A 64-year-old woman with a 25-year history of severe hypertension (never adequately controlled) presents with sudden onset of severe headache, blurred vision, and confusion. Blood pressure is 235/145 mmHg. Urinalysis shows 2+ protein and microscopic haematuria. Serum creatinine has risen from 1.4 to 5.2 mg/dL in 3 days. Fundoscopy shows papilloedema and flame haemorrhages. Renal biopsy shows hyperplastic arteriolosclerosis ('onion-skin' lesion) with luminal obliteration, and fibrinoid necrosis of afferent arterioles. Which pathological sequence best explains the arteriolar fibrinoid necrosis seen in malignant hypertension?

A 68-year-old man with 30-year benign prostatic hyperplasia and progressive bilateral hydronephrosis presents with bilateral flank pain and rising creatinine (now 4.2 mg/dL). CT shows massively dilated bilateral ureters and renal pelves, with cortical thinning bilaterally. He is catheterised, draining 800 mL of urine immediately. Over the next 48 hours, urine output is 4.5 L/day despite no diuretic treatment. Which tubular transport defect best explains this post-obstructive polyuria?

A 55-year-old female smoker presents with painless gross haematuria. Cystoscopy reveals a papillary lesion at the bladder trigone. TURBT specimen shows papillary transitional (urothelial) epithelium with mild nuclear atypia, no mitoses, and preserved polarity — classified as low-grade non-invasive papillary urothelial carcinoma (NMIBC, pTa). Three years after initial treatment she presents again with haematuria. Repeat cystoscopy shows a new flat, erythematous area in the dome. Biopsy shows high-grade dysplasia of the full thickness of the urothelium without invasion: carcinoma in situ (CIS). Which of the following best explains the different biological behaviour and malignant potential of these two lesion types?

A pathology specimen from a patient with end-stage renal disease secondary to reflux nephropathy shows a small, irregularly scarred kidney with coarse pitting of the cortical surface. Cut section reveals U-shaped cortical scars overlying dilated, blunted calyces. The scars are polar (upper and lower poles). A Year-2 student asks why the scars are specifically cortical and polar in distribution rather than uniformly involving the entire kidney. Which pathological mechanism best accounts for this specific pattern?

A 72-year-old man presents with left flank pain and painless haematuria for 2 months. CT scan reveals a 9 cm left renal mass with a 'staghorn' calcification filling the entire renal pelvis and calyces. The patient has a history of recurrent urinary tract infections with Proteus mirabilis. There is no metastatic disease on staging. Which mechanism best explains why this patient's renal stone type preferentially forms the staghorn configuration?