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Internal Medicine


Soft Rock – When Blasting It Doesn’t Work

Mark Schneider, MD

Providence Portland Medical Center – Portland, OR

Additional Authors: Jesse Powell, MD

Case-History of Present Illness: 68-year-old female presents with several days of malodorous urine and fevers. Brought to the ED by her daughter who diagnosed urinary tract infection (UTI) due to the distinct urine odor. No hematuria, dysuria, retention, or incontinence.

Past Medical History: Recent hospitalization for UTI with culture that grew P.mirabilis, completed course of cefdinir, with follow-up culture ordered by PCP that grew extended-spectrum beta lactamase (ESBL) E.coli.

Physical Exam and Vital Signs: Vitals: 115/48, 101, 38°C, 18, 93% without supplemental oxygen. • Lumbar spine tenderness, no CVA tenderness. Large area of erythema of right inner thigh and chronic lower extremity edema. Otherwise a non-focal exam.

Labs and Imaging: Procalcitonin 2.3, UA - packed bacteria/WBCs/3+ leukocyte esterase, WBC - 17.5, and urine culture with >100,000 CFU/mL ESBL E.coli. CT abdomen : Staghorn calculus within the lower pole calyces and renal pelvis of the right kidney. Heterogenous low density material within the mid and upper pole calyces suspicious for xanthogranulomatous deposits. Renal function evaluated via nuclear medicine kidney flow and function with diuretic showing: No urinary obstruction. Asymmetrical renal activity with 73% left kidney and 27% right kidney.

Clinical Course: IV antibiotics while undergoing work-up. Urology consulted and recommended stone removal due to recurrent UTIs with same organisms despite treatment. Went to OR for stone removal. Procedure abandoned due to unexpected finding of “white exudate renal collecting system mass” with concern for an organized abscess or fungal ball. Tissue sample sent for culture and pathology. Culture grew Proteus mirabilis/penneri. Pathology report stated degenerative amorphous material with rare inflammatory exudate and fibrinoid hemorrhagic exudate. Macroscopic appearance similar to picture at right. Patient readmitted for planned percutaneous nephrolithotomy. The stone was successfully removed by manual grasping and removal in pieces. Renal Matrix (Proteinaceous) Stones.

Rare: First described in 1908. 50 published cases between 1908-1981.

Risk Factors: Female. History of urinary tract infections, chronic renal failure, hemodialysis. • Infection with P.mirabilis or E.coli. Proteinuria.

Presentation: Similar to those with calcium nephrolithiasis – flank pain and UTI.

Diagnosis: Possible to suspect/diagnose by imaging. Usually made at the time of surgery.

Treatment Surgery: Surgical removal is necessary – emergently if obstruction or urgently for source control when associated with a UTI. Percutaneous or uteroscopic approach – Shockwave lithotripsy does not work.

Prevention of recurrence: Prophylactic antibiotic use. Acidification of the urine.

Conclusions • Rare and easily overlooked/mistaken for calcium based renal calculi • Diagnosis often at the time of surgery • Can cause obstruction and renal failure • Surgical/urologic intervention is needed for removal. Refractory to shockwave lithotripsy. • Antibiotics and/or acidification of the urine may help prevent recurrence.


Internal Medicine


Graduate Medical Education

Conference / Event Name

Academic Achievement Day, 2020


Providence Portland Medical Center, Internal Medicine Residency, Portland, Oregon

Soft Rock – When Blasting It Doesn’t Work