Impacted urethral stone presenting as urinary retention in a child

Abstract

A seven-year-old boy was referred to our Accident and Emergency department with a history of urinary retention secondary to urinary tract infection and an inability to pass a urethral catheter. He had been treated a month before for suspected pyelonephritis by the referring hospital. Attempts at urethral catheterisation failed, and he was taken to theatre for cystourethroscopy and catheter placement. At this time, an impacted urethral stone was discovered. Because it could not be dislodged, a suprapubic catheter was placed, and the child was brought back at a later date for definitive management. Investigations revealed a pure calcium oxalate stone that was secondary in origin. There has been no recurrence during a follow-up period of 6 months.

This illustrates that while rare, urethral stones do occur in children and should be considered in children presenting with urinary retention, haematuria and/or abdominal pain.

Background

Although the incidence of urolithiasis in children is much lower than in adults, and urethral stones, in particular, are uncommon, there are a sufficient number of reports in the literature to suggest that clinicians should be aware of this condition. Our case is a lesson that urolithiasis should be included in the differential of children presenting with abdominal pain, haematuria and/or urinary retention even without a preceding history of urinary tract infections (UTIs) or abnormalities.

Case presentation

His complaints consisted of dysuria, passing small amounts of urine, abdominal pain and distention. Although macroscopic haematuria was reported, there was none during admission. There was also no microscopic haematuria or bacteria evident on the urine dip and scope. He had never been treated previously in his life for urinary complaints. On examination, he was a healthy child with a distended lower abdomen and a palpable mass, in keeping with the bladder, extending to the umbilicus. Urethral catheterisation was attempted (eventually also under sedation as the child was traumatised from awake attempts and became uncooperative) and resistance was encountered in the posterior urethra. On palpation of the penis and perineum, no masses were felt. Immediately thereafter, he passed enough urine to relieve his discomfort.

Investigations

In terms of in-patient investigations, two urine cultures came back with no growth. One was done on admission and one during his stay while already on antibiotics. His admission total white cell count was 16.03×10⁹/L, creatinine was 55 µmol/L, calcium was 2.51 mmol/L and C reactive protein was <5 mg/L. An ultrasound demonstrated a small right kidney with scarring and thinning, particularly of the upper pole. Moderate hydronephrosis with a dilated proximal ureter was seen. The left kidney was normal. The bladder was also normal.

Diagnosis

A provisional diagnosis of acute urinary retention secondary to UTI was made.

Treatment

Intravenous antibiotics were started based on his previous presumed episode of pyelonephritis, diagnosed elsewhere, and it was hoped that as the infection was treated his difficulty in urinating would resolve.

He remained comfortable and passed urine spontaneously, with no recurrent distention of the bladder, in the following days until day five when he became distressed with abdominal pain and decreased urine output. He was taken to theatre for urgent cystourethroscopy with the intention to place a urethral catheter. At urethroscopy a stone was found in the posterior urethra (figure 1). It was obstructing the lumen, and it was not possible to either extirpate it or dislodge it proximally into the bladder. A suprapubic catheter was then placed.

Figure 1.

Impacted urethral stone found during urethroscopy.

Five days later, the child was taken back to theatre for laser ablation of the urethral stone. This was successful, and a urethral catheter was additionally placed. His postoperative course was uneventful and he was discharged without catheters and voiding spontaneously.

Outcome and follow-up

His stone analysis came back as calcium oxalate. A follow-up urethroscopy performed 1 month later demonstrated a well-healed urethra with no narrowing. He was followed up with a DMSA which demonstrated a small right kidney with minimal contrast uptake. The micturating cystourethrogram was normal.

Discussion

Paediatric urethral urolithiasis can be primary or secondary. There is usually an underlying anatomical abnormality in the case of primary stones, such as a urethral stricture or diverticulum.¹ This results in stasis and poor urine flow, allowing for precipitation and stone formation. A secondary stone is formed in the upper urinary tract, migrating downstream.¹ The stone may lodge and become impacted anywhere along the urethra, causing symptoms similar to a UTI or, as in the case of our patient, an outlet obstruction. Kit et al² suggested that recurrent stone formation is often due to a metabolic abnormality; however, this may vary depending on whether the patient is from an endemic or non-endemic region. This is because the literature suggests that risk factors for urolithiasis for children from endemic regions consist of a hot climate, diarrhoeal disease and malnutrition;³ while a study from the Netherlands, where stone disease is sporadic, revealed that 78% of children had an underlying metabolic disorder.⁴ There have also been reports in the literature of stones forming around non-absorbable sutures used in surgery of and around the bladder.⁵

An epidemiological study of paediatric nephrolithiasis in the UK showed that around half of patients present with either abdominal pain or macroscopic haematuria and only 30% with both.⁶ However, according to Gadelkareem et al,⁷ up to 90% of patients with stone disease have microscopic haematuria, so if this is detected in patients presenting with flank/abdominal pain and/or nausea/vomiting, stone disease should be actively ruled out. One should also consider urolithiasis in children with failure to thrive.⁶ Urethral stones in children typically present in one of two ways: sudden urinary retention without a clear preceding history of urinary tract complaints, due to their inability to express themselves; urinary retention following lower urinary tract symptoms.⁸ Urethral stones may also present with perineal or scrotal pain.¹ Although the presentation is typically acute, some patients may present with a longstanding history. Gadelkareem et al⁷ found at their institution that patients presented with a mean duration of 2 months. They attributed it to exogenous factors such as poor access to health and a low level of parents’ education. Such patients have a higher risk of presenting with end-stage renal failure.⁹

In retrospect, it is likely that our patient first presented with a kidney stone that was misdiagnosed as pyelonephritis. His second presentation was that of urinary retention due to secondary impaction of a passed kidney stone in the posterior urethra. Although stones in the posterior urethra are larger, urine can still flow around them.¹⁰ According to Kamal et al,¹¹ 88% of urethral stones that impact do so in the posterior segment. Interestingly, Akhtar et al¹² reported that in their series of 19 paediatric patients, 12 (63.1%) had stones in the anterior urethra.

It is not only underlying abnormalities that differ between developed and developing nations but also stone composition. Calcium-containing stones predominate in developed nations^2–4 while aluminium-containing stones predominate in developing nations.^{3 10} A major contributing factor is malnutrition. Diets high in cereal and low in calcium, phosphate and protein are acidogenic. Combined with high concentrations of urinary aluminium and urate, ammonium urate stones form.³ The reason for urate-containing stones has also been attributed to diarrhoeal episodes resulting in a loss of sodium, potassium and other electrolytes, as well as UTI with urease-producing bacteria.¹³ Our patient had a pure calcium oxalate stone. Stones of pure composition are less common than those that are mixed.³ Hypercalciuria is by far the the commonest underlying metabolic abnormality associated with urolithiasis, followed by hyperoxaluria and hypocitraturia.^{2 4}

Work-up includes a history of preceding gastrointestinal or urinary tract infections and previous urolithiasis and urinary retention episodes. Investigations should include urinalysis and culture to assess for haematuria and infection and imaging. Unenhanced helical CT scan is considered the gold standard for diagnosing urolithiasis² which involves radiation exposure. However, ultra-low-dose CT scans this may change and become more popular in the paediatric population. It is reasonable to start with a plain abdominal film as this will show radio-opaque stones and other causes of abdominal pain. Ultrasound can visualise the urinary tract well and, although unusual, can be used to image the penile urethra.^{1 10} Sometimes, as was the case with our patient, diagnosis may be made at endoscopy for urethral obstruction. In retrospect we should have performed lower urinary tract imaging to identify the cause of the failed urethral catheterisation and urinary retention. Had we identified the stone, we could have planned an earlier definitive intervention, preventing multiple anaesthetics and invasive procedures.

Following the trend of minimally invasive urological procedures in adults, they have been adopted in paediatrics with great success.¹⁴ In the case of urethral stones, the endoscopic options include urethroscopic extirpation or pushing the stone into the bladder if it is too large. The stone can then be safely removed by cystotomy¹⁵ or lithotripsy.¹⁶ Another option is laser ablation, which we used in our patient successfully and without complication. This is particularly useful in impacted urethral stones as it avoids the need for open surgery. Open surgery may still be necessary in children with anatomical abnormalities and those requiring correction of complications.^{10 14}

Learning points.

• Consider urolithiasis in children that present with haematuria and/or abdominal pain.

• Consider urethral stones in children that present with urinary retention and/or difficulty with urethral catheterisation.

• Urethral stones can present in children with normal urethrae and normal urological histories.

• Perform lower urinary tract imaging with failed catheterisation attempts or urinary retention.

• Securing a safe outflow for the urinary tract while leaving the definitive procedure to a urologist is acceptable and safe.