A 56-year-old man presented to surgery with new-onset urinary tract symptoms over the preceding week. These consisted of urgency and frequency associated with suprapubic pain. There was no frank hematuria. He had no significant past medical history and no history of STIs.Clinically he was afebrile and his abdomen was soft with no palpable bladder. There were no testicular abnormalities. A provisional diagnosis of UTI was made and the patient was prescribed a seven-day course of ciprofloxacin 500mg daily. His symptoms improved over the week and the urine microscopy report revealed no growth but large quantities of white and red blood cells.ReviewThe patient was reviewed at 10 days and was asymptomatic. A repeat urine microscopy was normal. At the review appointment, digital rectal examination revealed a non-tender benign prostatic enlargement. Biochemical tests including a PSA, glomerular filtration rate and U+Es were normal. Three weeks later he presented with frank hematuria and incontinence with lower abdominal and left-sided loin pain. He had a palpable bladder and a large stone trapped at the urethral entrance. He was admitted as a surgical emergency and underwent a meatotomy and stone removal under anesthesia. A cystoscopy was normal and there was no evidence of further calculi in the renal tract. The stone was calcium oxalate and thought to have originated from the ureter. A coexistent UTI had caused urethral impaction secondary to epithelial slough and an element of BPH. He has been well since.
Please provide a rationale with the answer.
What is the prevalence of ureteral stones?