This patient has acute flank pain and tenderness consistent with nephrolithiasis.  The pain associated with nephrolithiasis (renal colic) is often severe and, although it may wax and wane, is generally not positional.  The pain commonly radiates to the groin, especially as the stone passes down the ureter to the ureterovesical junction.  Nausea and vomiting are common, and bowel sounds are often diminished due to an associated ileus.  Hematuria is usually present but may not be grossly visible.

Most kidney stones are calcium-based (calcium oxalate, calcium phosphate).  But regardless of chemical composition, low fluid intake can lead to supersaturation of urine with crystalline material and promote stone formation.  Increasing fluid intake can reduce the risk of all types of stones.

(Choice A)  Excessive alcohol intake can trigger acute pancreatitis.  The pain associated with pancreatitis is typically located in the epigastric area rather than the flank and radiates to the back rather than the groin.

(Choice B)  Recurrent infections of the upper urinary tract with urease-producing organisms (eg, Klebsiella, Proteus) can lead to formation of magnesium ammonium phosphate (struvite) stones.  These stones are often large and may fill the renal pelvis.  Although patients may have mild flank pain due to recurrent infection, acute renal colic is uncommon as these large stones do not travel down the ureter.

(Choice D)  A high-fiber diet is associated with a decreased risk of diverticulitis.  This condition typically presents over a few days (not suddenly, as in this patient) with lower abdominal pain and tenderness in the left lower quadrant.

(Choice E)  Calcium passively follows the reabsorption of sodium and water in the renal tubules.  Increased dietary sodium intake leads to reduced sodium reabsorption in the proximal tubule and lowers calcium reabsorption (leading to hypercalciuria).

(Choice F)  Dietary calcium binds oxalate in the gut to form unabsorbable calcium oxalate.  Low-calcium diets lead to increased absorption of free oxalate, which is then excreted in the urine; the resulting hyperoxaluria promotes the formation of calcium oxalate stones.  Low-calcium diets are therefore paradoxically associated with increased risk of stone formation.

(Choice G)  Untreated infection with chlamydia or gonorrhea can lead to pelvic inflammatory disease, presenting with lower abdominal pain and fever.  Examination findings include mucopurulent cervical discharge and cervical motion tenderness.

Educational objective:
Urine supersaturation is the main mechanism underlying all types of renal stones.  Low fluid intake increases the concentration of stone-forming agents, thereby promoting stone formation.  All patients with nephrolithiasis should be advised to maintain adequate fluid intake.