Genitourinary tuberculosis refers to tuberculosis that develops in the kidney, ureter, testis, and epididymis through blood transmission [8]. Renal tuberculosis is the most common type of genitourinary tuberculosis and develops first. It then spreads from the kidney to the whole urinary system [9]. Therefore, renal tuberculosis actually represents the significance of urinary tuberculosis [10]. Renal tuberculosis is characterized by initial invasion of the renal cortex, development in the capillary plexus of the glomerulus, often involving the formation of multiple micro-tuberculosis foci, followed by progression to the medullary junction area and the renal papilla. Its growth and reproduction in the medulla were much more active than in the cortex, resulting in renal papillary ulcers and necrosis, until spread to the renal calices, resulting in cavitary ulcers. Damage to the renal structures occurs simultaneously with fibrosis during the repair process, leading to impaired renal function and obstruction [11]. Unilateral renal tuberculosis can cause ureteral stenosis, ureteral orifice lesions, and bladder contracture to cause ureteral dilatation above the lesion, and ureteral wall thickening, stenosis, and closure of the lumen can cause renal calcification, resulting in “ autonephrectomy.” Renal tuberculosis involving the contralateral ureteral orifice can cause contralateral hydronephrosis or contralateral kidney infection.

In patients with unilateral renal tuberculosis leading to nephrectomy or resection, when the disease affects the contralateral side, the lower discharge of necrosis in the kidney combined with the thickening and adhesion of the ureteral wall often cause ureteral obstruction and hydronephrosis. In severe cases, renal function markedly deteriorates. In our patients, renal function was impaired and serum creatinine levels increased to varying degrees. The serum creatinine and blood urea nitrogen levels decreased significantly 7 days after the operation, and there was no significant difference between the serum creatinine and blood urea nitrogen levels at 1 month after the operation and 7 days after the operation, indicating that the renal function of the affected side was protected by the operation, and the operation did not affect the renal function. The basic principle of the treatment of renal tuberculosis is systemic anti-tuberculosis treatment to achieve a cure and avoid surgery. However, most patients are already in the intermediate and late stages of the disease when diagnosed clinically, with ureteral stenosis and hydronephrosis, and the function and structure of the affected kidney are damaged to varying degrees [12]. Some scholars have reported that the rate of nephrectomy in patients with renal tuberculosis is more than 50% [13]. In patients who have undergone unilateral nephrectomy, the probability of renal tuberculosis on the contralateral side leading to renal function damage and subsequent uremia is very high [14]. Hence, it is particularly important to preserve residual renal function during this time. Ultrasound-guided percutaneous nephrostomy provides an alternative, which can directly drain the hydronephrosis or empyema of the tuberculous kidney and reduce or even terminate the stimulation of the ureter and bladder by tuberculous bacteriuria or pyuria. However, if the stricture of the ureter cannot be treated in the early stage of treatment, endoluminal treatment or surgical reconstruction is needed in the later stage. Regarding the outcomes of this group of patients, all patients received systemic standardized anti-tuberculosis treatment, of whom 11 patients had nephrostomy until the end of the follow-up period, and the longest time with the tube was 120 months. The nephrostomy tube was removed in another 14 patients, and eight of them underwent urinary reconstruction surgery, which indicated that nephrostomy afforded the time required for anti-tuberculosis treatment, provided opportunities for patients to undergo urinary reconstruction surgery in the future, and reduced the rate of kidney loss. If surgical reconstruction is still not possible or the patient is too old to tolerate surgery, long-term nephrostomy can also be an option.

As a common method for resolving urinary obstruction, ultrasound-guided percutaneous nephrostomy has the advantages of simple operation and a high success rate [15, 16]. A total of 63 punctures were performed in our patient population, and the success rate was 100%. Complications after nephrostomy include bleeding, infection, pain, adjacent organ injury, and fistula obstruction or detachment [17]. The reported incidences of severe and minor complications after puncture are 0–7% and 2–38%, respectively [18]. The highest critical values of the incidences of severe and minor complications recommended by the Royal College of Radiology were 8% and 15%, respectively [19]. The incidences of major and minor complications were 3.1% (1/32) and 9.4% (3/32), respectively, which were significantly lower than the maximum values recommended by the guidelines. There was one case of a severe complication in our patient population: perirenal hematoma after the puncture that improved after arterial embolization. Among the three cases with minor complications, there were two cases of gross hematuria with blood clot formation caused by bleeding at the puncture site. After treatment, the color of urine returned to normal within 72 hours after clamping of the nephrostomy tubeand repeatedly rinsing with sterile normal saline. In our experience, the technique to improve the success rate of puncture and reduce bleeding is to choose the shortest and clearest puncture path through the renal cortex, renal cone, and renal pelvis. While inserting the needle, the direction of the puncture was adjusted to ensure that the needle was accurately inserted per the predetermined path, and rapid continuous entry into the renal pelvis was avoided. One case of severe hemorrhage in our patient group was due to patient obesity; the needle path was not clearly displayed after the fourth puncture, which was caused by accidental injury to a large blood vessel in the kidney.

The complications related to nephrostomy tube mainly include nephrostomy tube obstruction, displacement, fracture, and detachment. All patients underwent long-term nephrostomy, and 12 (37.5%) developed complications related to the nephrostomy tube. According to the literature, nephrostomy tube shedding is the most common fistula-related complication. The incidence of nephrostomy tube shedding in the early postoperative period is approximately 1%, while that after the tube has been in for 1 month is approximately 2%. The incidence can be 11–30% if the tube is in for a longer time [20]. Regarding the nine cases of the nephrostomy tube falling off in our patient group, the tube was pulled out in all cases because of improper nursing by the patients or intolerable discomfort experienced by the patients. The most common cause of early postoperative fistula obstruction was gross hematuria and blood clot formation. Flushing the fistula with normal saline helped clear the obstruction. In our patient group, three cases of complete nephrostomy tube occlusion because of a large amount of caseous necrotic tissue in the tube, caused by renal tuberculosis, were noted. The 3-month replacement of the nephrostomy tubes based on the instructions for the use of the fistula tube. Long-term retention of the nephrostomy tube will reduce the frequency of replacement and the cost to patients. In this study, the coaxial guide-wire method was used to replace the drainage tube, and the success rate was 90.1% (310/344), which was relatively high. The main reason for failure was falling off of the nephrostomy tube owing to improper patient care or blockage of the nephrostomy tube and non-feasibility of guide-wire insertion. All patients could take care of themselves during the stoma period, which improved their quality of life.

Our study has some limitations. Due to the relatively rare cases of solitary kidney with hydronephrosis due to renal tuberculosis, the number of cases in this study is relatively small, and the assessment of complications is not comprehensive enough. Meanwhile, the changes of renal function in patients with long-term catheterization still need to be observed in large samples for a long time. Another limitation is that, since this procedure was performed by experienced interventional ultrasound physician, we couldn’t evaluate the impact of experience on technical success, and complication rates.