Gas-containing renal stone case report: A rare presentation

A 46-year-old lady presented to the Emergency Department with sudden onset left lumbar region pain and constipation. The patient’s history included a multiple, similar presentations of abdominal pain following an umbilical hernia repair 3 years ago and a history of renal calculi.

Contrast-enhanced CT of the abdomen and pelvis was performed on the same day of presentation looking for abdominal pathology to explain her pain. The study confirmed marked left hydronephrosis with multiple small and large stones within the dilated pelvicalyceal system with the largest stone approximately 3.4cm in the dilated upper calyx. Conglomerate stones in the pelvic ureteric junction cause obstruction (Figure 1). The rest of the study was unremarkable. There was also associated extensive perirenal stranding and a trace of fluid. The impression from the study was of obstruction and associated urosepsis. Stones were also noted to have air pockets within their structure (Figure 2) with no air within the pelvicalyceal system.

There are very few reported cases of gas-containing renal stones, with only 11 cases published describing the event. Over 60% of the cases had a urine culture growth of E. Coli with other cases growing Staphylococcus and Klebsiella [1]. The gas formation is theorized to be due to the metabolic activity of the microorganism from tissue metabolism [2]. The aetiology of gas in renal stone is still not determined but has been considered an early manifestation of emphysematous pyelonephritis (EP). EP is a severe infection of the renal parenchyma with a high mortality rate [5]. EP is more common in women (male-female ratio 6:1) and diabetics. Around 90% of cases are associated with poorly controlled diabetes, with other cases being associated with immunocompromised patients or cases with associated urinary tract obstruction secondary to renal stones, neoplasms, or sloughed papilla [6].

An abdominal x-ray can show gas within the renal shadow, but due to low sensitivity, it is not the ideal modality for diagnosis and follow-up. An ultrasound scan could show abnormalities with non-dependent echoes, but due to the adjacent location of bowel gas, it could lead to misdiagnosis [3]. The composition of a stone with gas is less dense as there are more fibrotic tissue, proteins, and necrotic cells which would affect the acoustic shadowing seen on ultrasound [4]. CT scan is the preferred investigation modality as it can be used to identify the shape, internal structure, and site of the stone without needing contrast material [5]. Early intervention with medical and surgical management produces a survival rate of more than 90 for patients with EP [8].

The patient was treated with IV antibiotics, cystoscopy, and a left ureteric stent insertion and discharged with planned percutaneous nephrolithotomy (PCNL). However, the patient returned with flank pain and fever. The urine culture grew E. coli, and the patient was treated with tazocin for emphysematous pyelonephritis. A left-sided nephrostomy stabilised her condition, and an urgent PNCL was planned shortly after.

Important learning points:

• Gas in renal stone can have life-threatening complications if not identified early and treated appropriately.
• Emphysematous pyelonephritis is one of the complications associated with gas in renal stone which is predominantly caused by E. coli.
• Patients presenting with a similar scenario and sepsis will need urgent drainage preferably with nephrostomy to target more effective kidney drainage, followed by urgent stone clearance once the septic condition stabilizes.

Written informed patient consent for publication has been obtained.