Acute Postoperative Pulmonary Thromboembolism as a Result of Intravascular Migration of a Pigtail Ureteral Stent

Abstract

We report an unusual case of acute, early postoperative pulmonary thromboembolism as a result of extreme intravascular migration of a pigtail ureteral stent with probable wedging of its tip into a pulmonary arterial branch. Case Report A 29-yr-old, 57-kg, 171-cm woman was subjected to pyelolithotomy under general endotracheal anesthesia. Her medical history included left kidney agenesis, two episodes of pyelonephritis within the past 3 mo, and mild (Grade 1) hydronephrosis. Before surgery, the clinical examination, electrocardiogram (ECG), and chest radiograph (CXR) were unremarkable; serum creatinine and 2-h creatinine clearance were 1.4 mg/dL and 65 mL/min, respectively. The operation included right flank incision, removal of a large coral calculus from the renal pelvis and ureteropelvic junction via an intrahilar incision, antegrade placement of a self-retaining, 6F, 26-cm long, pigtail ureteral stent (Fig. 1), and closure of the pelvic wall and surgical wound. Before insertion, the surgeons confirmed that the stent’s tip was intact and that its distal curl exceeded 180°(1).Figure 1: Intraoperative abdominal radiograph after placement of the self-retaining pigtail ureteral stent. The proximal curl of the stent (thick white arrow) is located at the level of the right kidney, whereas its distal curl and tip (thin white arrow) are situated within the ring of the pelvis and, thus, probably within the urinary bladder as well.On emergence from anesthesia, coughing occurred. After tracheal extubation, the patient was referred to the postanesthesia care unit. Vigorous coughing (4 to 5 episodes of 1–2 min duration) occurred within the first 2 postextubation hours. Postoperative analgesia was patient controlled with IV fentanyl. Patient status was deemed as satisfactory during the first 12 postoperative hours (Table 1); she lay supine on her own preference. However, within the following hour, she complained of shortness of breath and “mild to moderate” pleuritic pain of sudden onset over the left lower hemithorax. Monitored variables indicated clinical deterioration (Table 1). Chest auscultation revealed diminished breath sounds and expiratory wheeze over the left lower hemithorax.Table 1: Monitored Patient Variables: The Presented Values Were Recorded Within 30–60 Minutes Before and Within 10–20 Minutes After the Onset of Dyspnea and Chest PainSupplemental oxygen (inspired fraction, 0.31) was started. Diagnostic speculations included pulmonary embolism (small to moderate probability) (2,3), pneumonia (small probability because of the absence of high fever), and left ventricular ischemia (minimal probability) (4). A 12-lead ECG, transthoracic echocardiography, and an anteroposterior CXR were ordered (3). The ECG revealed only sinus tachycardia (115–120 bpm), a finding compatible with our first two speculations (3,5). Transthoracic echocardiography (performed by a cardiologist) revealed a foreign body within the right heart and pulmonary artery trunk. Mild tricuspid and pulmonary valve insufficiency were present, but there was no concomitant evidence of right ventricular pressure and volume overload (3). The CXR revealed that the pigtail ureteral stent was actually within the heart, with its distal portion extending into the left pulmonary arterial tree; left lower lobe atelectasis was also noted (Fig. 2).Figure 2: Emergency anteroposterior chest radiograph revealing a pigtail catheter with its proximal half forming a loop within the right heart and its distal half extending into the left pulmonary arterial tree. The thick white arrow points toward the pigtail catheter tip. Reduction of left lung volume with leftward displacement of the cardiac shadow and obscuring of its left border (thin white arrows) was also noted. Additional findings included attenuation of the left costodiaphragmatic angle, probably because of the presence of a pleural effusion (black arrows).The potential for retroperitoneal hemorrhage secondary to stent-induced vessel erosion was excluded by contrast-enhanced abdominal computed tomography. The stent was retrieved via the right femoral vein with vascular retrieval forceps. Subsequent pulmonary angiography revealed a filling defect of the left posterior-basal pulmonary arterial branch. Any pre-removal potential fragmentation of the stent was excluded by matching it to another, unused, 6 French, 26-cm-long pigtail catheter. Subcutaneous enoxaparin (30 mg twice daily) was started (6). Subsequent recovery was uneventful, with eventual dissipation of symptoms. Average daily urinary output was >1.5 mL · kg−1 · min−1. Two-hour creatinine clearance measured 96 mL/min on postoperative Day 3. Postanesthesia care unit and hospital discharge occurred on postoperative Days 7 and 14, respectively. After normalization of the follow-up lung perfusion scans, enoxaparin was discontinued (postoperative Day 60). Discussion Urologists routinely use pigtail stents to relieve or prevent ureteral obstruction. Frequent stent-induced complications are loin discomfort, hematuria, dysuria, trigonal irritation, development of hydronephrosis, urinary tract infection, and stent migration, fragmentation, and occlusion (7–10). Rarely reported adverse events include perforation of the renal pelvis, ureteropelvic junction, and renal vein; erosion through the ureteral wall into the abdominal blood vessels or bowel; and formation of fistulae (7,11–13). However, our search of the National Library of Medicine database (http://www.ncbi.nlm.nih.gov/entrez; key words, “ureteral stent”; limits, none; number of articles retrieved, 1266) revealed that the complication report-ed herein has not been described in the indexed literature. The stent’s erosion into the renal vein after perforation of the renal pelvis or proximal ureter was unlikely, because after the probably correct antegrade placement, the stent’s proximal curl was directed opposite to the renal vein’s anatomical location (Fig. 1) (14). Stent rotation and migration toward the urinary bladder would be required for such a complication to occur. However, the reviewed literature suggests that distal stent migration is very rare. Also, the erosion of a major vein would probably have resulted in significant retroperitoneal hemorrhage, a possibility excluded by our computed tomography findings. Consequently, the stent probably entered the systemic circulation via one of the two intercommunicating ovarian veins, most likely just distal to the site where these vessels cross the anterior wall of the distal third portion of the ureter (14) (Table 2).Table 2: Speculated Step-by-Step Mechanism of the Reported Complication and Potential Contributing FactorsThe reported complication probably occurred in a stepwise manner, as shown in Table 2. Low stent/ureter length ratio (15), small stent size (6 French), the shape of the stent’s distal portion, ureteral wall trauma and fragility secondary to prior passage of renal calculus fragments or the stent itself, and emergence coughing leading to abrupt increases in intraabdominal pressure could have been important contributory factors. Before initial insertion, the surgeons confirmed the stent’s functional integrity. The empirical selection of stent size was aimed at achieving its atraumatic passage via an inflamed ureteropelvic junction. However, the stent/ureter length ratio was not predetermined, as recently recommended (15). After insertion, the anatomical positioning of the stent was estimated with an anteroposterior abdominal radiograph (15) and was considered as “probably correct” (Fig. 1). Thus, further determination of stent’s positioning with a lateral abdominal radiograph or cystoscopy (to visually confirm the intrabladder location of the stent’s distal curl) (15) was considered unnecessary. During the recovery period, the endoscopic placement of a second ureteral stent was avoided, because urinary flow was evidently unobstructed. Finally, after hospital discharge, enoxaparin therapy was continued as recommended (16). In conclusion, our case presentation shows that after pigtail ureteral stent-using urologic procedures, the potential for pulmonary arterial branch obstruction secondary to the stent’s intravascular migration should be considered in the differential diagnosis of postoperative dyspnea and/or chest pain. We wish to thank Dr. Vassilios X. Boursinos for offering helpful advice.