A 57-year-old man comes to the hospital due to nausea, vomiting, and severe crampy pain in the right flank. He has had no fever or chills. Several days ago, the patient had similar, but less severe, pain that resolved spontaneously. Medical history is significant for type 2 diabetes mellitus, obesity, hyperlipidemia, hypertension, and gout. Temperature is 37 C (98.6 F), blood pressure is 160/100 mm Hg, and pulse is 98/min. Physical examination shows right flank tenderness. Blood urea nitrogen and serum creatinine are normal. Abdominal ultrasound reveals right-sided hydronephrosis and proximal ureteral dilation. Urinalysis in this patient would most likely reveal which of the following?

Question

A 57-year-old man comes to the hospital due to nausea, vomiting, and severe crampy pain in the right flank.  He has had no fever or chills.  Several days ago, the patient had similar, but less severe, pain that resolved spontaneously.  Medical history is significant for type 2 diabetes mellitus, obesity, hyperlipidemia, hypertension, and gout.  Temperature is 37 C (98.6 F), blood pressure is 160/100 mm Hg, and pulse is 98/min.  Physical examination shows right flank tenderness.  Blood urea nitrogen and serum creatinine are normal.  Abdominal ultrasound reveals right-sided hydronephrosis and proximal ureteral dilation.  Urinalysis in this patient would most likely reveal which of the following?

Quizplus · Accepted Answer

This patient has acute, recurrent flank pain associated with ureteral dilation; this presentation is typical for acute ureterolithiasis. Although ultrasound is relatively sensitive for ureteral and calyceal dilation due to an obstructing stone (hydronephrosis), small stones themselves may not be visible. Kidney stones usually cause disruption of the ureteral epithelium with resulting gross or microscopic hematuria due to the presence of free red blood cells (RBCs) in the urine. When bleeding into the renal collecting system or lower urinary tract occurs, RBC morphology is normal. In contrast, glomerular bleeding (eg, glomerulonephritis) causes formation of RBC casts due to trapping of RBCs by precipitating Tamm-Horsfall protein (Choice C); the cells are typically dysmorphic due to mechanical and osmotic trauma as they pass through the nephron. Inspection of urine sediment in patients with acute ureterolithiasis may identify crystals corresponding to the type of stone. This patient has risk factors for uric acid stones, including gout and metabolic syndrome (obesity, diabetes mellitus, hyperlipidemia), and urinalysis may show polygonal uric acid crystals (which are morphologically distinct from the needle-shaped monosodium urate crystals seen in synovial fluid in acute gout). (Choice A) Malignant cells can sometimes be identified on unstained microscopy of urine sediment in patients with urothelial carcinoma arising from the epithelium of the renal pelvis, ureters, or bladder. However, these malignancies typically present with painless hematuria rather than acute ureteral obstruction. (Choice D) Urine specific gravity correlates with urine concentration, and a specific gravity of ≤1.003 indicates dilute urine; because kidney stones most commonly occur in concentrated urine (eg, >1.015), it is unlikely that a patient with an acute stone would have such a low specific gravity. (Choice E) Occasional white blood cells may also be seen in ureterolithiasis, but overt pyuria suggests a urinary tract infection; white cell casts would be more characteristic of renal inflammation or infection (eg, acute interstitial nephritis, pyelonephritis). Educational objective: Urine sediment in acute ureterolithiasis typically shows free red blood cells (hematuria) and crystals consistent with the type of stone. Ultrasound can reveal ureteral and calyceal dilation (hydronephrosis), but small stones themselves may not be visible.

A 57-Year-Old Man Comes to the Hospital Due to Nausea