A surfacing staghorn: Spontaneous expulsion of a large renal calculus from a nephrocutaneous fistula

Case presentation

An 83-year-old female presented with discomfort and a hard palpable swelling from a chronic sinus in the loin. Past medical history was noteworthy for type 2 diabetes mellitus, chronic kidney disease (CKD 3) and chronic obstructive pulmonary disease (COPD). On examination, she had a visible sinus at the right flank where her pain was located and a stone was seen to be protruding through to the skin (Figure 1).

Figure 1.

Photograph of loin sinus with nephrocutaneous fistula. Evidence of purulent discharge. The calculus can be seen to be extruding.

From a urological perspective, she was known to have a nephrocutaneous fistula for many years, which had been managed conservatively with nephrostomy bags to collect any purulent discharge. She had been seen on a regular basis in the urology outpatient unit for the preceding decade. She had a non-functioning, chronically infected right kidney containing a large staghorn calculus. She had been previously offered surgical treatment which she declined at the time. Cross-sectional computed tomography (CT) imaging performed in 2017 revealed two large stones present in the sinus tract, which was leading to an atrophic right kidney (which in itself was bearing a large degree of calcification). The left kidney at that time appeared morphologically unremarkable.

Blood tests during her acute presentation revealed marginally elevated inflammatory markers, with a white blood cell count of 12.7 (10⁹/L), neutrophils of 10.3 (10⁹/L) and C-reactive protein of 41 mg/L. Her renal function was stable, with a creatinine of 113 µmol/L and eGFR of 39 mL/min. Her clotting screen was within normal limits.

A non-contrast CT scan of the kidneys, ureters and bladder was performed to characterise the anatomy and establish the stone burden (Figures 2 and 3). This revealed a scarred right kidney and the presence of a staghorn calculus. There was a nephrocutaneous fistula present, and the stone could be seen very superficially.

Figure 2.

Non-contrast computerised tomography of the kidneys, ureter and bladder (CT KUB): coronal slice revealing right-sided staghorn with nephrocutaneous fistula and erosion of calculus to skin surface.

Figure 3.

Non-contrast CT KUB: axial slice revealing right sided staghorn with nephrocutaneous fistula and erosion of calculus to skin surface.

Intravenous co-amoxiclav was commenced empirically after blood and urine samples were sent for culture. Analgesia was prescribed for symptomatic relief. Following CT imaging, the stone was percutaneously manually extracted on the ward without any immediate complications (Figure 4). The remaining discharging sinus was covered with a bag to collect any purulent discharge. Following a period of observation, she was discharged from hospital with a course of oral co-amoxiclav.

Figure 4.

Photograph of the extruded staghorn calculus.

District nurse referral was made for ongoing wound management in the community following hospital discharge. She was followed up in the urology outpatient clinic one month after hospital admission. At that time, the loin sinus tract was seen to be granulating well. Following the extraction of a stone during the acute admission, a further stone was extruded percutaneously (which the patient brought with her to her clinic appointment). No follow-up imaging has been arranged. A quarterly nurse-led clinic has been booked to assess her ongoing progress.

Discussion

Urolithiasis is an important health issue, causing major clinical and economic burden. ¹ Estimates of global incidence are as high as approximately 10%. ² Evidence from the UK Hospital Episodes Statistics database suggests that there is a rising prevalence of kidney stone disease and its associated interventions. ²

Staghorn calculi are large stones that fill the renal pelvis and calyces, and they are associated with significant morbidity and mortality. ³ Symptoms of staghorn nephrolithiasis include haematuria and flank pain. If left untreated, of particular concern is the risk of chronic infection, which can result in chronic pyelonephritis, xanthogranulomatous pyelonephritis, pyonephrosis and/or renal abscess. There is also the risk of insidious, progressive renal failure.

Surgical treatment for staghorn nephrolithiasis includes percutaneous nephrolithotomy (PCNL)±extracorporeal shock wave lithotripsy or ureteroscopy and laser lithotripsy, or nephrectomy in a non-functioning kidney for suitable surgical candidates. Achieving stone-free status is not straightforward, with many patients requiring multiple or staged procedures. ⁴ PCNL complication rates range from 20% to 83%, ⁵ and it can be a high-risk intervention for the elderly patient with multiple co-morbidities. The most common reasons for conservative management are co-morbidities and lack of fitness for general anaesthetic (GA), patient choice, poor access and anatomical factors. ⁶

Seminal papers by Singh and Blandy^7,8 compared the outcomes of patients with staghorn calculi who underwent pyelolithotomy versus conservative management. In their retrospective study, they observed inferior outcomes with conservative management (morbidity and mortality from infection, renal failure and ultimately need for nephrectomy). They concluded that surgical intervention was almost always indicated.

A recent literature review found 10 studies (total of 304 patients) observing the outcomes of patients with staghorn stones managed conservatively. ⁹ They found that progressive renal deterioration occurred in a mean of 27.5% cases, with a higher rate among bilateral staghorn patients (44% vs. 9%). Dialysis was required in 9% of patients (20% bilateral, 41% unilateral). Disease-specific mortality ranged from 0% to 67%.

Nephrocutaneous fistulae are a sequela of chronic infection on a background of nephrolithiasis and are uncommon in the developed world. They develop due to chronic inflammation or infection of the kidney that progresses through Gerota’s fascia and subcutaneous tissue. It is more commonly seen in patients who have had prior surgical intervention (e.g. nephrectomy or PCNL). There are a small number of isolated case reports of spontaneous nephrocutaneous fistulae. The most frequently reported causes of spontaneous nephrocutaneous fistulae in the literature were staghorn calculi or multiple renal stones^10–21 associated with infection, particularly xanthogranulomatous pyelonephritis.^10,14,15,17 Other less common causes reported included ureteric stones, ²² renal tuberculosis^18,23 and renal replacement lipomatosis.

On review of the literature, many patients presented in a similar manner to our patient, with an intermittently discharging lesion from the flank where on examination one or multiple sinuses could be seen.^{10–14,16–23} Some had subcutaneous swellings that had increased in size prior to rupturing.^17,21 Duration of symptoms varied from 3 months to 14 years.^14–23

There are very few cases reported of spontaneous expulsion of renal stone via a fistula tract. One reported by Purkait et al. is of a four-year-old girl with a staghorn renal calculus that expulsed into the psoas muscle ¹³ and another by Puthenveetil et al. of a 45-year-old man with xanthogranulomatous pyelonephritis who had spontaneous expulsion of multiple small stones via a nephrocutaneous fistula. ¹⁴ Both these cases were reported in India. To our knowledge, our case is the first of spontaneous expulsion of a renal stone of this size to be reported in the developed world.

Rubilotta et al. suggested an algorithm for investigating and managing nephrocutaneous fistula. ²⁴ They recommend abdominal CT as a first line investigation. In the developed world, this is a quick, affordable and reliable option.

Initial treatment for nephrocutaneous fistula when discussed in the literature has included antibiotic therapy or in the case of obstructing ureteric calculi, ureteroscopy and extraction of stone.^{10,11,15,16,22} However, almost all patients proceeded to nephrectomy and excision of the fistulous tract, as imaging revealed a non-functioning kidney. One case was managed by an open nephrolithotomy, calyceal fulguration and drainage of the perinephric abscess, ²⁰ and another was managed conservatively due to other co-morbidities in a 90-year-old. ¹⁵

Conclusion

In conclusion, staghorn nephrolithiasis can result in recurrent urosepsis and progressive renal failure if not managed surgically. Conservative management of staghorn disease may be appropriate in select patient groups: those with multiple co-morbidities at high risk for GA, in cases of patient refusal of surgery or in patients with aberrant anatomical factors.

Nephrocutaneous fistula is a complication of chronic kidney infection, and spontaneous extrusion of stone is a rare, late complication of conservatively managed disease. To our knowledge, this case is the first of spontaneous expulsion of a renal stone of this size to be reported in the developed world.