Ureteral obstruction is one of the most common urological emergencies, the etiology of which can be benign (in case of ureteral stones or strictures secondary to surgery or radiotherapy) or malign (when a urothelial cancer affects the ureteral lumen or when an abdominal advanced neoplastic disease compresses the ureter ‘ab estrinseco’) (1). Effective treatment should be immediately carried out, in order to avoid the complications of long-term obstruction (such as pain, infection and ultimately renal failure). The scope of this treatment is to alleviate the patient pain and to protect its renal function (2). To date, the most commonly used existing surgical methods for ureteral obstruction include percutaneous nephrostomy (PCN) and Double J stenting (DJS) (3,4). PCN is performed under both sonographic and fluoroscopy guidance. This procedure requires the patient to be in the prone position and moderate sedation is needed. PCN placement is associated with a risk of hemorrhage, urinary tract infection and catheter dislodgement. On the other hand, DJS placement is performed concomitantly with cystoscopy for the visualization of the ureteral orifice, with the patient who is in the supine position during the procedure. Early complications of DJS placement include irritative bladder symptoms, hematuria and stent discomfort; meanwhile, stent migration and encrustation are among the common complications in the late period. The selection of the drainage method is multifactorial and may be influenced by the nature of each case, considering different factors such as complexity, local technique expertise, availability of medical equipment and patient features. For example, the classical ureteral obstruction is due to stones; about this, we have to consider that in certain health systems the waiting time for stone removal surgery is long. For this reason, it was observed that an expected long period time for definitive treatment biased the treating urologist to prefer a ureteral stent over nephrostomy tube, assuming the patient would be less bothered by the stent during the waiting period. Currently, no existing guidelines suggest to the urologist the ideal treatment for the obstructive uropathy. On one hand, DJS placement is commonly considered as the best surgical method, but it can occasionally be difficult to apply in patients with cancer. On the other hand, the numerous complications associated with the PCN procedure must be considered. The treatment choice for patients with obstructive uropathy is, therefore, still an open question. Both procedures have advantages and disadvantages in regard to complications, costs and post-operative management. Therefore, it is important to select the appropriate technique, as each has its own unique impact on the patients' outcomes. For this reason, it was assessed which of the two main methods is superior in this type of patients according to normalization of renal function indices, post-operative complication and the perception of the quality of life by the patient's point of view.

In a period between 2019 and 2023, a total of 317 consecutive patients (198 males and 119 females) presenting to the emergency room of our hospital with a ureteral obstruction, which was resolved surgically by DJ stent placement or nephrostomy tube, were enrolled in the present study. All patients signed a written informed consent. All data analyzed were collected as part of routine diagnosis and treatment. Patients were treated according to national and international guidelines and agreements. Surgical drainage was performed when definitive treatment was not possible immediately or when a two-stage procedure was considered a safer approach. Inclusion criteria were: Ureteral obstruction with fever (>38˚C), acute renal failure (indicated by an increase in creatinine and urea nitrogen blood values), risk of sepsis (suspected based on an increase in WBC count) or intractable pain. Diagnosis of the ureteral obstruction was made by either a non-contrast CT and/or renal ultrasound. Pregnant women and patients with a contraindication to either form of drainage (for example uncorrected coagulopathy excluding percutaneous tube, hemodynamic instability precluding anesthesia for DJS placement or abnormalities of the urinary tract) were excluded from the analysis. Patients received either a DJS or a PCN according to the surgeon's preference and to the availability of anesthetic support. PCN was routinely performed in local anesthesia (1% Lidocaine, 10 cc), positioning a percutaneous pigtail polyurethane 8 or 10-French catheter (Cook medical). Ureteral stents were placed under loco-regional anesthesia and according to the commonly validated technique; a 6 or 7 FR, Percuflex (Boston Scientific) stent of the appropriate length (most commonly from to 24-28 cm) was used. Specifically, 155 patients of the study sample were treated with nephrostomy, whereas 217 individuals underwent to stenting procedure. The standardized Clavien-Dindo classification of surgical complications was used to assess and report post-operative complications (5). According to Clavien classification, post-operative complications were subdivided in three grades as shown in Table I. The PCN group was composed of 79 men (mean age ± standard deviation: 58.17±16.21 years, min-max: 39-92 years) and 76 women (mean age ± standard deviation: 60.18±14.34 years, min-max=29-90 years), whereas the DJS group constituted of 116 men (mean age ± standard deviation: 68.53±10.88 years, min-max=18-92 years) and 101 women (mean age ± standard deviation: 64.01±15.94 years, min-max=23-85 years). Notably, the legal age of adulthood in Italy is 18 years. For each participant, data concerning the creatinine (mg/dl), azotemia (mg/dl), potassium (mEq/l), WBC count (10³/mm³), core temperature (˚C), pain in the side (yes or not), anti-inflammatory therapy (yes or not) and ASA score were evaluated. The pre- and post-drainage data of creatinine, azotemia, potassium, WBC count and core temperature are reported in Table II. The distribution of the flank pain and of the anti-inflammatory therapy pre- and post-drainage until 4 days after the intervention separately for the DJS and PCN groups are reported in Fig. 1. In both groups the post-procedural pain was measured with VAS scale, suggesting a higher pain in patients with DJS. The VAS scale corresponds to the visual representation of the extent of the pain felt by the patient and is made up of a predetermined line 10 cm long, where the left end corresponds to ‘no pain’ while the right end corresponds to ‘worst possible pain’. Patients in the present study were asked to draw a mark on the line representing the level of pain they felt. The scale line can be oriented horizontally or vertically, without this affecting its sensitivity; however, the horizontal orientation was preferred. The scale was administered to patients 24 h after the surgical procedure and in the following days, until discharge. Thereafter, measurement was performed weekly for a 6-month follow-up. The score was calculated in mm, measuring with a ruler the length of the line between the end corresponding to the minimum intensity and the mark placed by the patient. Based on several studies, the following cut-off values were used: 0 to 4 mm: ‘no pain’; from 5 to 44 mm: ‘mild pain’; from 45 to 74 mm: ‘moderate pain’; and from 75 to 100 mm: ‘severe pain’.

Consistently, patients with DJ stents reported values on the VAS scale, which oscillated between moderate pain and severe pain. By contrast, a greater number of patients with PCN reported not complaining of any pain. Furthermore, quality of life (QoL) was assessed weekly after the surgical procedure for a 6-month follow-up period. Patients were requested to fill out the ‘Tube symptoms’ questionnaire' which included six questions regarding pain, analgesics use, hematuria, urinary discomfort, discomfort associated with movement and discomfort associated with personal hygiene. Answers to these questions were based on a four-point rating scale; a higher score is associated with worse symptoms. At each measurement, the DJS group more frequently reported pain, analgesics use and presence of hematuria. Furthermore, the severity of these symptoms increased over time in the DJS group, while patients with PCN showed greater adaptation to the surgical device, which did not impede their personal hygiene or carrying out their daily activities.

The medial length to defervescence was 2.06 days, while the median length of white blood count (WBC) normalization was 1 day. After discharge, none of the patients undergoing DJS placement required readmission to the hospital; conversely, 10 patients (6,4%) required readmission to the hospital due to PCN dislocation. More patients with DJS presented to the emergency room with complaints related to their procedure compared with patients with PCN, mostly due to flank pain and dysuria. The post-drainage complication rate was not similar, being higher in PCN group. The majority of patients in both groups underwent ureteroscopy as the definitive treatment. The length of time between the urgent drainage and the definitive treatment was higher in the DJS group compared with the PCN group; this meant that a greater number of patients with DJS were admitted to the emergency room due to infection, malfunction of the stent or calcification of the same in both the bladder and the kidney (with the consequent need for a double operation, percutaneous nephrolithotomy and laser cysto-lithotripsy, to remove the stent in those patients).

The incidence of ureteral obstruction has risen in last decades for causes that differ depending on the age group of the patients: Ureteral stones in young and middle age (6) while, for the elderly, advanced urological malignant diseases (such as bladder cancer which involves ureteral orifice or ureteral neoplasms) or non-urological abdominal cancer with compression of the ureter are more common (7). Those patients require emergency treatment in order to avoid different adverse events such as pain unresponsive to medical therapy, urinary infections, acute renal failure, urosepsis and even death (1). Despite the commonness of these situations, only few studies compared renal drainage methods (8-12). The placement of PCN or DJS represents the mainstream surgical drainage method for temporary relief of obstruction (13). However, the dilemma of choosing between these two drainage methods remains extremely relevant and current in urological daily practice; this is where the idea of our research was born. In the present study, all patients were potential candidates for both procedures and they showed similar characteristics. The goal of the aforementioned systems is to obtain ureteral drainage, in order to maintain renal function, waiting for the resolution surgery. Regarding this, some studies reported a difference in time to second procedure (9), which was 2-fold longer in DJS patients compared with those with PCN (probably because a patient with a DJS is mistakenly considered less debilitated compared with a patient with a PCN). Furthermore, both PCN and DJS placements have some complications such as the risk of infection and displacement, as well as the discomfort of nephrostomy catheter and stent. Moreover, ureteral stents should be exchanged every 6 to 8 weeks in order to avoid the risk of encrustation and bacterial colonization (14). Generally, stent placement has a high success rate and it is minimally traumatic using the natural ureteral orifice. In addition, it does not require an external tube, resulting in no effect on the aesthetic appearance of patients. However, the review of Ramsey et al (15) suggested that retrograde stent placement leads to increased bacteremia. PCN placement reduces renal pelvis pressure and the risk of bacteremia (16). It is commonly performed under local anesthesia by a urologist using ultrasonographic guidance (16) and, in part for this reason, urologists consider PCN to be superior to DJS (17). Likewise, oncologists were more likely to recommend PCN as the next step after stent failure in unilateral obstruction (18). In another study a more rapid return of serum creatinine to normal levels with PCN tubes than DJS was also reported (19). Moreover, unstable patients with larger stones being severely ill should be treated with PCN under local anesthesia (12). Despite this, in clinical practice, the proper surgical option is affected by numerous factors. In recent decades, studies (evaluating the superiority of one drainage method over the other) reported inconclusive results, probably due to too small study samples. Thus, PCN and DJS were compared to understand which of the two was the best drainage method for resolving urinary tract obstruction. The Chi-square test showed a not significant difference in the incidence of complications according to sex (Chi-square=0.692; P=0.4054), whereas a significant difference was assessed regarding the incidence of the complications according to the type of intervention (Chi-square=13.000; P=3x10^-4), highlighting a higher incidence of complications in the nephrostomy group. The paired t-tests demonstrated a statistically significant improvement of the patients' condition after the intervention for both nephrostomy and stenting, as reported in Table I. Moreover, the independent samples t-test showed a significant difference between the variations of the several metrics considered (values of the creatinine, azotemia, WBC count and body temperature) when comparing the nephrostomy and the stenting operations, highlighting a higher effect of the nephrostomy, as showed in Table II. On the other hand, compared with DJS, PCN showed a relatively higher rate of post-operative complications. Another aspect that was evaluated is the QoL of patients undergoing DJS placement or nephrostomy tube. Both surgical methods caused pain or discomfort to a significant number of patients. Generally, while the number of patients with PCN complaining of pain remain similar over time and with an ever-decreasing use of analgesics, more patients with DJS report of pain, requiring greater and more frequent use of painkillers (20). The most troublesome symptoms in the DJS group are irritative symptoms of the lower urinary tract (10,21), inflicting ~70% of these patients who require over time a higher number of emergency room visit due to the unchanged frequency and severity of the bother symptoms. In distinct opposition, patients with PCN suffered at first mostly from discomfort during daily activities and personal hygiene but, over time, they adjusted to this condition. This result is corroborated by the study of de Sousa Morais et al (10) and in other studies which compared PCN drainage vs. DJS in other clinical scenarios (22,23). Although according to the current results PCN is superior to DJS for temporary urinary diversion in terms of renal function preservation (with also an improved QoL for the patients, as demonstrated by the results of the VAS scale and of the ‘Tube symptoms' questionnaire’), the choice of treatment depends on the individual situation. For example, PCN represents the choice treatment in case of advanced malignancies, after failed retrograde stent placement (24) and in patients who might not be able to tolerate general anesthesia (25). Thus, the decision on the appropriate method of drainage is multifactorial; furthermore, a discussion with the patient is extremely important because the urologist might explain the clinical advantages and the complications of each procedure, not forgetting what is expected regarding tube symptoms and their impact on QoL. To quote Dr Louis R Kavoussi (26), ‘traditionally, urologists have placed stents because … that's what we do’, but his experience is that ‘patients are more comfortable with a nephrostomy than a stent’. The results of the present study support superior QoL of nephrostomy tube over time, inducing some urologists to reconsider their choice of renal drainage, especially in health systems in which definitive treatment might be delayed. There are several limitations to the present study. Selection bias may have been introduced through choice of drainage procedure according to surgeon's preference, with a higher probability of performing PCN in patients suspected of long-standing obstruction. Furthermore, as different imaging modalities were used (CT scan and/or ultrasonography exam), hydronephrosis severity could not be assessed as a possible confounder. Nevertheless, the authors consider that the present study has a fundamental strength. To the best of our knowledge, the current research represents the first single-center study with the highest number of patients enrolled, which allows for a more accurate assessment of the problem of ureteral obstruction.

In conclusion, according to the present results, PCN is an improved method compared with DJS for management of ureteral obstruction in terms of renal function preservation, also ensuring an improved QoL (as demonstrated by the results of the VAS scale and of the ‘Tube symptoms' questionnaire’). Moreover, patients with PCN have a higher rate of postoperative complications. Then, concerning the prediction of the hospitalization time (according to the two-class classification: hospitalization time lower or higher than 3 days), the test accuracy of the prediction was 61.9% for DJS and 60.2 for PCN. These results demonstrate the feasibility of predicting the hospitalization time for the patients based on their pre-drained condition. Although the results are preliminary and the accuracies are not high, this approach could help the surgeon choose the right kind of intervention for each patient. In fact, predicting hospitalization time is directly related to post-surgery complications, which can significantly impact patient outcomes and healthcare resource management. To improve the accuracies obtained, it could be possible to include more regressors for the machineries (for example, detailed patient demographics, comorbidities, lab results, imaging findings and intraoperative details). Furthermore, increasing the sample size can enable models to learn improved patterns and generalize well to unseen data. Additionally, increasing the sample size would allow to employ more sophisticated ML algorithms or ensemble methods that can capture more complex patterns in the data.