A 49-year-old woman comes to the emergency department for evaluation of back pain. The patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy for ovarian cancer 1 week ago. She had an uncomplicated postoperative course, with her Foley catheter removed on postoperative day 2. She was discharged home on postoperative day 4. The patient noted some right-sided back pain after surgery that improved with pain medications. However, the pain has become progressively more severe and is no longer responding to pain medications. The pain does not radiate, and now she has associated nausea and vomiting. Temperature is 37.2 C (99 F), blood pressure is 128/72 mm Hg, and pulse is 92/min. BMI is 38 kg/m². The abdominal incision is closed and has no erythema, drainage, or fluctuance. There is mild right costovertebral angle tenderness; the left side is nontender. Serum creatinine is 0.8 mg/dL. Catheterized urinalysis is normal. Which of the following is the most likely cause of this patient's pain?

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11ec25c8_d961_44ce_bc81_69623c6bf7c0_MD0003_00 This patient's postoperative, unilateral back pain; nausea with vomiting; and costovertebral angle tenderness are most likely due to hydronephrosis from ureteral injury. Gynecologic surgery, particularly hysterectomy, has the highest risk for iatrogenic ureteral injury due to the proximity of the ureters to the pelvic organs, particularly the uterine artery. Risk of ureteral injury increases in patients with obesity, distorted pelvic architecture from malignancy (as in this patient), or prior pelvic surgery (eg, cesarean delivery). Ureteral injury most commonly occurs due to accidental suturing of the ureter during uterine artery ligation or vaginal cuff closure, which can cause partial or complete ureteral obstruction. Patients with ureteral obstruction develop hydronephrosis; however, symptoms can be masked initially by postoperative pain medications. With continued obstruction, patients have nonradiating back pain and costovertebral angle tenderness. Because only 1 ureter is affected, patients typically have normal renal function (eg, normal creatinine and urinalysis); however, irreversible renal damage can occur if the obstruction is untreated. Diagnosis can be made by renal ultrasound. Treatment is surgical correction of the obstruction (eg, suture removal). (Choice A) Acute pyelonephritis may present with costovertebral angle tenderness, and it is a complication of recent Foley catheter use. However, patients with pyelonephritis typically have fever, chills, and an abnormal urinalysis (eg, bacteria, red and white blood cells). (Choice C) Nephrolithiasis can present with unilateral back pain and nausea/vomiting; however, patients typically have pain that radiates to the groin and microscopic hematuria on urinalysis, making this diagnosis less likely. (Choices D and E) Renal vein thrombosis and subsequent unilateral renal infarction can occur in patients in a hypercoagulable state (eg, malignancy). In acute cases, patients can develop back pain and costovertebral angle tenderness; however, these patients typically have hematuria. Unilateral ureteral injury is the more likely diagnosis in this patient given her progressively worsening back pain beginning immediately after surgery. Educational objective: Ureteral injury presents postoperatively with ureteral obstruction and subsequent hydronephrosis (eg, nonradiating focal back pain, unilateral costovertebral angle tenderness). Without prompt diagnosis and treatment, irreversible renal damage can occur. References: Prevention of ureteral injuries in gynecologic surgery. (http://www.ncbi.nlm.nih.gov/pubmed/12748497)

A 49-Year-Old Woman Comes to the Emergency Department for Evaluation