Spontaneous passage of a 5 cm ureteric calculus: A case report and review of the literature

Abstract

Ureteric calculi larger than 10 mm rarely pass spontaneously, and current guidelines recommend active intervention beyond this threshold. We report a 62-year-old woman who presented with obstructive pyelonephritis secondary to a 5.4 cm by 0.8 cm proximal ureteric calculus. Following antibiotic therapy and a staged surgical plan, the stone migrated distally over several months and was spontaneously passed 92 days after initial presentation, after only two weeks of alpha-blocker therapy. To our knowledge, this is the first reported spontaneous passage of a ureteric calculus exceeding 5 cm, challenging existing assumptions regarding stone diameter and passage likelihood.

1. Introduction

Ureteric calculi are a common urological condition, with a lifetime prevalence of urolithiasis estimated at 10-12% in men and 5-7% in women.¹ The majority of stones that present with renal colic are less than 10 mm in size. The spontaneous passage rate is inversely proportional to stone size; calculi larger than 10 mm have a passage rate approaching zero without intervention.² While there are isolated reports of patients passing stones up to 14-17 mm,³ the spontaneous passage of a calculus exceeding 5 cm is, to our knowledge, previously unreported. We present the case of a 62-year-old female who successfully and spontaneously passed a 5 cm ureteric calculus, an event that challenges conventional understanding of ureteral physiology.

2. Case presentation

A 62-year-old female presented to the emergency department with a several-month history of episodic, dull right lower back pain, which had acutely intensified alongside 3 days of chills and rigors. She denied fever, haematuria, dysuria, or lower urinary tract symptoms. Her past medical history was significant for a right hemithyroidectomy for a nodular goitre in 2014, with no history of childhood urological conditions or metabolic stone disease.

On examination, she was hemodynamically stable, alert, and comfortable. The only positive finding was right flank tenderness with a positive right renal punch. Bedside ultrasonography revealed right-sided hydronephrosis. Laboratory investigations showed a leucocytosis (12.3 × 10⁹/L), elevated C-reactive protein (176.7 mg/L), and an elevated serum creatinine of 78 μmol/L with an estimated glomerular filtration rate (eGFR) of 80 mL/min/1.73m². Urinalysis was positive for pyuria (>225 WBCs), microscopic haematuria (174 RBCs), and 1+ bacteria; however, the subsequent urine culture was negative.

A contrasted CT scan of the abdomen and pelvis demonstrated a large, 5.4 cm × 0.8 cm obstructing calculus (822 Hounsfield Units) in the right proximal to mid-ureter at the L5-S1 level, causing moderate upstream hydroureteronephrosis (Fig. 1). Diffuse patchy hypo-enhancement of the right kidney with mild perinephric stranding was suggestive of superimposed acute pyelonephritis. Additionally, urothelial thickening and enhancement with adjacent fat stranding in the proximal ureter indicated concurrent pyelitis.

Fig. 1.

Initial CT scan showing 5.4 cm obstructing proximal ureteric calculus with hydronephrosis.

The clinical diagnosis was right-sided obstructive pyelonephritis and pyelitis secondary to a 5.4 cm ureteric stone. The patient was managed with intravenous hydration, analgesia, and empiric antibiotics (IV Cefazolin and a single dose of IV Gentamicin). Percutaneous nephrostomy tube insertion was not considered as the patient was not septic at presentation, and to reduce the need for multiple procedures. Her inflammatory markers and renal function improved with supportive management. After three days of inpatient stabilization, she was discharged on a 2-week course of oral Amoxicillin-Clavulanate. The definitive initial operative plan was an elective laparoscopic ureterolithotomy following the resolution of the infection. Medical expulsive therapy with alpha-blockers was not initiated at this stage.

An interval CT Urography, performed 2.5 months later to guide the planned surgery, revealed distal migration of the stone to the right vesico-ureteric junction (VUJ) (Fig. 2). Persistent findings included unchanged moderate hydronephrosis with renal cortical thinning, delayed nephrographic and pyelographic phases, and persistent urothelial thickening. Three days after this scan, the patient was assessed in the outpatient clinic. She reported a 1-week history of new-onset dysuria, though a repeat urine culture remained negative. Given the stone's distal migration to the VUJ, the surgical plan was revised to add on a retrograde ureteroscopy with laser lithotripsy to the initial operative plan, as the stone might have extruded out of the ureteric orifice. She was also started on Tamsulosin 0.4 mg daily to help with ureteric access.

Fig. 2.

Interval CT scan showing stone migration to the vesico-ureteric junction (VUJ).

Remarkably, one week before her scheduled surgery (approximately 2.5 weeks after the clinic visit), the patient presented reporting spontaneous stone passage. She described dysuria during the event but no flank pain, fever, or visible haematuria. The passed calculus was brought to the medical team and photo-documented, confirming a true length of 5 cm (Fig. 3). This represents a 92-day interval from the initial emergency presentation to spontaneous passage, with only 2 weeks of alpha blockers.

Fig. 3.

Photograph of the 5 cm passed calculus with measurement scale.

A follow-up CT Urography three weeks after passage confirmed the absence of the distal calculus. It showed interval improvement in hydronephrosis, with near-complete resolution of the distal hydroureter, with residual mild dilatation of the renal pelvis and upper ureter. The patient remained asymptomatic and was discharged from urological follow-up with a plan for community-based renal function monitoring.

3. Discussion

This case is unique due to the unprecedented size of a spontaneously passed ureteric calculus into the bladder, and then again through the bladder neck out of the urethra, representing 2 discrete events deemed to be of very low likelihood. The patient passed a 5 cm, high-density (822 HU) stone without endoscopic or surgical intervention, a feat not documented in modern urological literature. To put this in context, a 2018 systematic review by Yallappa et al.⁴ found that for stones >10 mm, the spontaneous passage rate was negligible, and guidelines universally recommend active treatment for ureteral stones >10 mm.⁵

Several physiological and pathological factors may have contributed to this outcome, transforming a seemingly impossible event into reality. Firstly, the stone's morphology was unique. While 5 cm in length, its width was only 0.8 cm. This long, slender configuration is highly unusual and was likely moulded by the ureteral lumen over time. The passive ureteral dilatation caused by chronic, partial obstruction, as evidenced by the hydroureteronephrosis and cortical thinning, likely created a capacious conduit. This luminal remodelling could have aided the stone's gradual distal migration.

Secondly, the clinical timeline suggests a multi-step process rather than a single acute event. The initial diagnosis was of an obstructing proximal stone with pyelonephritis. The inflammation-induced pyelitis and ureteritis, visualized as urothelial thickening and fat stranding, may have paradoxically facilitated passage. We hypothesise that the intense mucosal oedema, combined with systemic antibiotic therapy to resolve the active infection, created a lubricated, less spastic ureteral environment. This inflammatory milieu may have allowed the stone to disimpact from its proximal location and migrate distally over the 2.5 months. The initiation of Tamsulosin after the stone reached the VUJ likely played a supportive role in relaxing the intramural tunnel for the final phase of expulsion, a mechanism well-supported for distal stones.⁶

Whilst these processes may have contributed to the eventual spontaneous expulsion of this calculus, the true mechanism is still indeterminate and warrants further evaluation.

This case challenges the dogma that calculus length alone dictates spontaneous passage. While guidelines focus primarily on the maximal stone diameter, our patient's longitudinal stone axis was parallel to the ureteral axis. This orientation minimizes the cross-sectional obstructive burden, making spontaneous passage mechanically plausible in a chronically dilated system. It is a critical reminder that a single axial measurement on CT may not fully capture the clinical behaviour of an atypically shaped calculus.

The primary management lesson is the critical importance of source control before definitive stone management. The initial decision to prioritize antibiotics and an interval, staged surgical plan allowed for the safe resolution of her pyelonephritis and pyelitis. This non-operative window, combined with the medical expulsive therapy, inadvertently and safely led to the spontaneous resolution of a condition initially deemed to require a laparoscopic or endoscopic procedure.

4. Conclusion

This case represents the first report of a spontaneously passed 5 cm ureteric calculus. The passage was likely multifactorial, resulting from a favourable stone orientation (long and slender), chronic ureteral remodelling from long-standing obstruction, and a stepwise medical approach that first controlled infection and later provided alpha-blockade. This report expands our understanding of the biomechanics of ureteral stone passage and underscores that maximal stone diameter may not fully predict outcome in unusually shaped calculi.

CRediT authorship contribution statement

Ashwin Singaram: Writing – original draft, Visualization, Investigation, Data curation, Conceptualization. Jeffrey J. Leow: Writing – review & editing, Supervision, Conceptualization.

Ethics declaration

Written informed consent to take part in the study and to publish the article has been obtained from all participants or their legal representatives. The privacy rights of participants have been observed.

This study was performed in compliance with relevant laws, regulatory frameworks and guidelines where the research took place. Ethics committee approval was not required under relevant laws and institutional guidelines. This is a retrospective case report describing routine clinical care of a single patient. In accordance with institutional policy at Tan Tock Seng Hospital, formal ethics committee review is not required for single case reports that do not involve a research protocol or experimental intervention. Informed consent for publication was obtained from the patient.

This research follows the CARE guidelines and the CARE checklist.

Patient consent and ethical approval

Informed consent was obtained from the patient for publication of this case report and accompanying clinical images. Formal institutional ethics committee approval was not required for the publication of this single case report, in accordance with institutional policy.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.