Clinical History
A 68-year-old male presented with fevers and rigors. He had a 6-month history of intermittent bilateral flank pain and haematuria. Blood tests showed significantly impaired renal function with normal serum calcium. CT abdomen revealed bilateral hydronephrosis with multiple renal calculi and perinephric and subphrenic abscesses. The patient later died due to progressive renal failure.

Pathology
The kidney specimen is grossly enlarged and partially bisected. There is marked dilatation of the pelvi-calyceal system. Renal tissue is significantly atrophic, sometimes reduced to a thin rim. A large mottled brown-white calculus is present in the pelvis, and a smaller calculus obstructs the ureter lumen. The ureter is dilated proximal to the obstruction. Multiple calculi are visible within the calyces.

Further Information
Urolithiasis affects up to 1 in 10 individuals during their lifetime. Stones form anywhere along the urinary tract but most commonly in the kidneys. Risk factors include male gender; conditions affecting urine composition such as hypercalciuria or hyperoxaluria; systemic metabolic disorders like cystinuria or gout; dietary factors including high oxalate and animal protein intake as well as low fluid intake; and environmental factors such as hot dry climates. Although 80% of renal calculi are unilateral, this patient had bilateral stones.

Symptoms include colicky, severe, and paroxysmal pain, haematuria which can be gross or microscopic, nausea, vomiting, fainting, dysuria, and urgency. These symptoms often appear when stones move into the ureter.

There are different types of renal calculi. Calcium stones, which make up about 70% of all stones, are composed of calcium oxalate or calcium phosphate and are caused by hypercalciuria, hypercalcemia, or hyperoxaluria. Struvite stones account for 5-10%, consisting of magnesium ammonium phosphate, often due to Proteus infections, and can form large staghorn calculi. Uric acid stones also make up 5-10% and occur in patients with hyperuricemia such as gout or chronic leukemias. The remaining stones are cysteine stones, caused by impaired renal reabsorption of amino acids like cystine.