Bowel Perforation after Extracorporeal Wave Lithotripsy: A Review of the Literature

Introduction: Extracorporeal wave lithotripsy (ESWL) is considered a first-line treatment for renal and ureteral stones up to 10–20 mm in diameter. Complications are uncommon, with a reported rate of 0–6% in the literature. Bowel perforation has only been described in a few case reports but requires rapid diagnosis and treatment. Methods: A review of the literature from PubMed/Medline, Embase, Cochrane, and Web of Science databases was performed including studies reporting bowel perforation secondary to ESWL between January 1990 and June 2022. Results: We found 16 case reports of intestinal perforation in the literature. Although some patients had previously undergone abdominal surgery or had inflammatory intestinal disease, others were without comorbidities that could lead to complications. Abdominal pain was the main symptom and imaging was required to confirm the diagnosis, which usually necessitated a surgical intervention. As regards the ESWL technique, it appears that the combination of a high energy level and the prone position constitutes a risk factor for these rare complications. At the authors’ centre, only one case has been reported among 24,000 ESWL procedures over 20 years: A 59-year-old female who underwent ESWL for a distal right ureteral stone presented acute abdominal pain and free intraperitoneal pelvic fluid on ultrasound. A CT scan revealed a small bowel perforation requiring open laparotomy with primary closure. Conclusions: In conclusion, although bowel perforation after ESWL is rare, progressive abdominal pain with tenderness at physical examination requires proper imaging evaluation to exclude bowel perforation and prompt intervention if required.


Introduction
Since its introduction in the 1980s [1], extracorporeal wave lithotripsy (ESWL) has been shown to be a safe, effective, and non-invasive treatment for renal and ureteral stones up to 10-20 mm in diameter [2]. In the last two decades, ESWL technology has evolved, especially as regards the quality of shock wave generators, coupling, and stone location, making it possible to optimize results while reducing failure rates [1,3].

Methods
A review of the literature was performed from PubMed, Medline, Embase, Cochrane and Web of Science databases including studies published between January 1990 and June 2022. Two reviewers (A.F. and S.F) conducted the research in the databases previously mentioned. The search was performed by using the combination of the words "ESWL" and "bowel" or "intestinal" and "perforation" or "complications" and "urinary" or "urologic" and "stones". Those keywords led to 16 results in which ESWL for urologic stones were complicated by colonic or small bowel perforation.
A data analysis was performed to evaluate risk factors and preventive measures.
Twelve patients were male, three were female, and one was of unknown gender. Patient age ranged from 29 to 78 years.
The interval between the ESWL procedure and the onset of symptoms varied between a few hours and 2 days. All patients presented at the emergency department with a main complaint of acute abdominal pain with tenderness at physical examination. Moreover, fever was present in one-third (5/15) of the cases.
During the 1990s, a KUB X-ray was performed for diagnostic imaging, whereas since then CT scan has been the main diagnostic tool.
A surgical approach with bowel repair was needed in 15 cases due to the high morbidity of intestinal perforation or hemodynamic instability. The remaining case was managed conservatively without further complications; this treatment strategy was chosen because the patient was hemodynamically stable without signs of peritonitis.
The location of the perforation varied according to the ESWL treatment area. In six of the sixteen cases [14,15,17,18,20,22], the perforation occurred in the colon, while in the remaining nine cases the small bowel was affected.
Regarding the stone location prior to ESWL, there was only one renal stone [20], with ureteral stones being the most common. Eight studies reported stone size, and in only one case was the stone larger than 10 mm [27].
The prone position was used in 11 cases, a combination of prone and supine in one, and supine in two [14,16]; in two studies the position was not reported. The total number of shocks delivered varied from 2500 to 6000. Table 2 summarizes the ESWL characteristics.
At the authors' institution, just one case of bowel perforation has been reported after 24,000 ESWL procedures performed over 20 years; this patient needed open surgery and primary closure of the wound, as further discussed below.

Discussion
The incidence of bowel perforation after ESWL is unknown. Our literature review revealed reports of only 16 cases, although cases of gastrointestinal damage other than perforations have been described in single case series. These other complications have included gastric or duodenal erosions, ureterocolic fistula, gastrojejunal anastomotic dehiscence, small bowel obstruction and strangulation, cecal ulcers, sigmoid colon hematoma, peripancreatic hematoma, peripancreatic abscess, pancreatitis, and rectal bleeding [14,28,29].
Interestingly, most cases of intestinal perforation after ESWL are seen in males, and patient age varies greatly. The predominance of male cases can perhaps be ascribed to the higher incidence of urolithiasis in the male population. Although some of the patients that we identified had a medical history of abdominal surgeries or intestinal inflammatory disease, most had no relevant past medical history or risk factors. Nonetheless, patient selection should be made carefully, or complications are likely to occur in these cases.
In this review, in the vast majority of cases (13/16) only one ESWL session was performed before intestinal perforation occurred. However, in one case it was reported that the stone was initially in the renal pelvis, where the first ESWL session was conducted [12]. Additionally, in two other cases [19,20] more previous ESWL sessions were described but it was not clearly specified if they were performed for the same stones. The interval from the procedure to the onset of symptoms varied between a few hours and 2 days, with the typical presentation being acute abdominal pain with tenderness at physical examination. Patient's management was surgical from the beginning in 12 cases because of clinical signs of peritonitis [12][13][14]17,18,20,21,24,27]. Only in four cases [19,22,23,25] was conservative management with antibiotic initially preferred. In three of them, due to clinical worsening, patients had to undergo surgery between 24 and 48 h. In the other case [19], the patient remained hemodynamically stable and a control CT scan was performed at 7 days with signs of improvement.
Finally, there was one case [16] where obstructive stones was first suspected, so a double J stent was placed. Then, due to clinical signs of peritonitis, a CT was performed revealing signs of bowel perforation, so the patient finally underwent surgery.
Therefore, a surgical approach with bowel repair was required in all cases except one patient [19]. There were no fatal outcomes and clinical recovery after surgery was complete.
ESWL treatment can affect either the small bowel or the colon, depending on the stone location. In our review, the mean stone diameter was 8.2 mm, and in only one case did the stone diameter exceed 10 mm. As regards the ESWL technique, it appears that the combination of a high energy level and the prone position constitutes a risk factor for these rare complications.
The single case of bowel perforation after ESWL at the authors' institution, where 24,000 ESWL procedures have been performed over the past 20 years, was in a 59-year-old female with a past medical history of dyslipidemia, chronic bronchitis, and a C-section. Initially, in the context of colic lumbar pain, she had been diagnosed as having a 17 mm right distal ureteral stone at her referring hospital. As the patient presented with moderate hydronephrosis, a right nephrostomy tube was placed, and she was referred to our centre for definitive treatment of the stone. Three weeks later, under sedation, she underwent a first ESWL session, resulting in partial fragmentation. The patient was placed in the supine position on a Lithoskop lithotripter (Siemens, Munich, Germany), which delivered 4500 shocks to the stone with a total energy of 175 joules.
Four hours after the procedure, the patient returned to the emergency department due to discomfort and intense right abdominal pain. Physical examination revealed painful palpation and localized tenderness at the flank and right iliac fossa. A blood test showed 15,000 × 10 9 /L leukocytosis with neutrophilia (82%). She did not present fever, but abdominal pain was worsening despite analgesia. An abdominal ultrasound revealed a small amount of free intraperitoneal fluid. A CT scan with contrast was performed, resulting in the diagnosis of a small bowel perforation at the level of the terminal ileum with free abdominal fluid and a small amount of pneumoperitoneum.
The general surgery department evaluated the case and suggested exploratory laparoscopy, which revealed diffuse purulent peritonitis with possible perforation in the mesenteric margin of the terminal ileum as well as a hematoma in the mesojejunum and two lesions in terminal ileum serosa close to the main lesion. As the lesions could not be clearly assessed, the decision was taken to perform a mini-laparotomy, which confirmed the perforation identified by laparoscopy. Simple closure was performed without intestinal resection.
During the postoperative follow-up, the patient remained hemodynamically stable and afebrile, progressively tolerating an oral diet. She was discharged from the hospital 5 days after the intervention. Follow-up at the first month was unremarkable. Two months later, a right ureteroscopy with laser dusting of the stone and double J stent placement was performed without abnormal intraoperative findings. During endoscopy, no alterations of the ureteral wall were found. Three weeks later, the double J stent was removed, and the patient has since been stone free with no complications.
Risk factors for bowel perforation due to ESWL reported in the literature are previous abdominal surgery, prone position, placement of the ureter too close to the intestine, and the use of high energy levels [14].
Prompt diagnosis of a bowel perforation is crucial to avoid further complications. Initial physical examination to assess abdominal acute pain and tenderness should be complemented with a general blood test and the performance of a CT scan. Once the diagnosis has been established, surgery seems to be an effective treatment, with good patient recovery. Stone treatment can be offered at the same time with ureterotomy and stone removal, but in most cases, treatment is deferred.

Conclusions
Although bowel perforation is rare, and renal colic is the main complication after ESWL, patients with acute abdominal pain few hours after the procedure should undergo a proper physical exploration to search for peritoneal irritation. Furthermore, it usually requires accurate imaging evaluation. Imaging may enable the physician to rule out an intestinal complication or to initiate prompt intervention if required, bearing in mind the high morbidity of the condition. The combination of a high energy level and the prone position seems to constitute a risk factor for this rare complication.  Data Availability Statement: Data was extracted directly by the cited publications and by analysing our case report.

Conflicts of Interest:
The authors declare no conflict of interest.