Multiple preputial stones: A case report and literature review.

Highlights • Preputial stones are a very rare form of urinary tract stone.• Almost all the cases happen in a male in uncircumcised males, poor genital hygiene, low socioeconomic status, and phimosis.• The symptoms and signs are due to phimosis.• Neglected preputial stones can cause serious morbidities, such as hydronephrosis and renal failure.


Introduction
Preputial stones are a very rare form of urinary tract stone, and few cases have been reported in the literature [1], occurring especially in uncircumcised males [2] with poor genital hygiene, and low socioeconomic status [3]. The first report of a preputial stone in an adult was by Robert Clarke in 1794 [4]. Preputial stone is primarily regarded as a result of severe phimosis; other causes are smegma solidification and accumulation of urine flow on the preputial area [1]. Here we report a case of an adult male with multiple preputial stones, in line with the updated consensus-based surgical case report (SCARE) guidelines [5].

Case presentation
A 50-year-old man came to an outpatient clinic with the chief complaint a mass at the tip of the penis and progressive difficulty voiding for the past year, with a history of passing a stone on 48 occasions. Vital signs were within normal limits. On physical examination, the prepuce appeared to be phimosis and was palpable, with a thick preputial skin and stone inside the preputial cavity ( Fig. 1). On upper tracts ultrasound, serum creatinine level and other biochemical parameters were within normal limits. Urinalysis revealed 10-14 leukocytes/high-power field (HPF) on microscopic examination. A plain film and urethrography x-ray showed multiple radio-opaque shadows in the tip of the penis, with a normal caliber of the urethra, and no evidence of stricture (Fig. 2). Dorsal slit circumcision and preputial stone extraction were done (Fig. 3), recovering 134 stones of up to 4 × 8 mm (Fig. 4). The stone analysis revealed 44% carbonate apatite phosphate, 38% ammonium urate, 10% amorphous calcium phosphate carbonate, and 8% matrix (unknown matter).

Discussion
Preputial stones can occur at any age but are far more common in adult males [6]. In Indonesia, childhood circumcision is a traditional practice; which likely accounts for this being the first reported case of preputial stones in Indonesia. All cases of preputial stone are associated with severe phimosis in uncircumcised males [1]. Stones usually occur singularly or as a few; only five cases have reported the presence of more than 100 stones ( Table 1).
The symptoms and signs are due to phimosis, which causes urinary stasis beneath the foreskin [3]. In some cases, the urinary obstruction can be severe, causing obstructive uropathy [6]. Preputial stones might be associated with complications, such as dysuria, stranguria, hematuria, and preputial ballooning during    voiding, rarely with urinary retention [2], obstructive uropathy, foul-smelling discharge from prepuce [6], and preputial skin fistula [1]. Metabolic evaluation can provide clues about the cause of stone formation, especially in a situation where the stone is found in the other parts of the urinary tract, such as the kidney, ureter, and bladder (KUB) [6]. The stones are often palpable on examination of the prepuce; however, a plain radiograph can confirm the existence [7]. Ultrasound or KUB, or both, are essential to rule out any proximal stones, as the treatment will be either minimally invasive (e.g., shock wave lithotripsy) or involve endoscopic or open surgery [7].
Wilford characterized preputial stones according to their pathogenesis [3]: 1) inspissated smegma with lime salts, 2) struvite composition secondary to an infection, and 3) stone formed in the proximal urinary tract, which is trapped during migration. Winsbury-White characterized preputial stones by their composition [3]: 1) inspissated smegma, 2) smegma and urinary salts, 3) and urinary salts alone. In our case, the stones were mostly composed of carbonate apatite phosphate and ammonium urate, thus indicating a combination of a nidus of smegma acting as a condensation nucleus for the precipitation of urinary salts and urinary tract infection. Smegma is an accumulation of cellular debris in the preputial fold and has a dual role in preputial stone formation [8]. In addition to functioning as a nidus, smegma can be a direct irritant, inducing inflammation, adhesions, and preputial stenosis, and leading to obstruction with stasis [3]. Treatment involves the removal of stones and elimination of the predisposing cause [7]. As in this case, the patient underwent a dorsal slit circumcision procedure to remove the stone. Neglected preputial stones might cause serious morbidities, such as hydronephrosis and renal failure secondary to obstructive uropathy [1,7] and preputial skin fistula [1] (Table 1).

Conclusion
Preputial stones occur primarily in adults with phimosis and poor hygiene. Factors contributing to urinary tract stone formation, including obstruction, stasis, infection, and nidus deposition, are implicated in the genesis of preputial stone. Our findings