ureteropelvic junction obstruction

Boy With Sharp, Colicky Abdominal Pain

Children’s Hospital of The King’s Daughters

Dr Weaver is a third-year pediatric resident at Children’s Hospital of The King’s Daughters in Norfolk, Va.

Alexander K. C. Leung, MD—Series Editor: Dr Leung is clinical professor of pediatrics at the University of Calgary and pediatric consultant at the Alberta Children’s Hospital in Calgary.


A 7-year-old boy with sharp, colicky left-sided abdominal pain that began 6 hours earlier during school hours. He vomited once about 15 minutes after the onset of pain and 3 times while waiting in the emergency department. The pain had decreased without any treatment but remained constant. The patient had no fever or chills and no urinary frequency, urgency, or dysuria. He denied a history of trauma. His most recent bowel movement was nonbloody, soft, and painless. He led a healthy, active childhood and had no prior hospitalizations or surgeries.


Afebrile, well-hydrated patient noted to be grasping his left flank. Blood pressure, 127/85 mm Hg; heart rate, 148 beats per minute, with regular rhythm. He had brisk capillary refill. Lungs clear to auscultation. Abdomen smooth and nondistended, with consistent softness. Bowel sounds present in all 4 quadrants. No bruits or hums appreciated. Liver was within rib margin, with no splenomegaly, rebound, or guarding. Deep palpation of the left anterior side of the abdomen resulted in radiating pain into the left inguinal region and significant left-sided costovertebral angle tenderness. No palpable abdominal or scrotal hernia. Testes descended bilaterally and nontender, with normal coloration.


A basic metabolic panel revealed normal electrolytes. A plain abdominal film showed moderately increased stool burden but otherwise normal findings. Urine was clear yellow, with specific gravity of 1.02 and pH of 5.5; it was negative for protein, glucose, and ketones and positive for 25 to 50 red blood cells per high power field.

An order was written to strain all urine, and the patient was given a normal saline bolus in an effort to help wash out a presumed stone. An ultrasound examination was performed in an effort to visualize potential calculi (findings shown).


The ultrasound images showed kidney size disparity, with the left kidney measuring 4.5 cm larger than the right. Marked dilation of the left renal calyces and pelvis was noted (Figure 1). The bladder wall appeared to be of normal thickness. The presence of hydronephrosis and left-sided kidney enlargement led to consideration of an obstructive process, such as ureteropelvic junction (UPJ) obstruction, ureretrovesical junction
obstruction, or posterior urethral valves.

A noncontrast spiral CT scan of the abdomen and pelvis revealed marked left pelvicaliectasis with abrupt transition to a nondilated proximal left ureter near the UPJ. The presence of perinephric fluid along the medial lower pole suggests an acute obstruction. A renal calcification was not identified.


UPJ obstruction is the most common congenital abnormality of the urinary tract and is usually caused by intrinsic stenosis.1 It is estimated to occur in 1 per 1500 newborns with antenatal hydronephrosis and is diagnosed in about half of these babies on further workup.2 About 60% of cases involve the left side. There is a 2:1 to 3:1 male-to-female ratio. The vast majority of cases pre-sent in the neonatal period. This case is unique in that the patient was 7 years old at presentation.


The cause of UPJ obstruction may be intrinsic (eg, incomplete recanalization during embryologic development or abnormal neurogenic/muscular peristalsis) or extrinsic. Extrinsic causes include the following:

High insertion of the ureter at the renal pelvis that results in impaired drainage.

Crossing lower pole renal vessels or impingement on ureteral flow by a vessel.

Anatomic blockage from a tumor.

Renal ectopy or hypermobility causing intermittent obstruction.

A stone.

Postsurgical obstruction from scarring.3

The genetics of smooth muscle hypertrophy as a cause of UPJ obstruction is an ongoing investigation in mouse models.4


Most UPJ obstruction cases are discovered early because of routine ultrasonography done in the prenatal period. About 50% of infants with prenatal hydronephrosis have UPJ obstruction.5 Most infants with UPJ obstruction appear healthy, although a neonatal flank mass may be appreciated. Older children with UPJ obstruction may present with urinary tract infection, hematuria, abdominal pain, and abdominal distention. Acute ureteral obstruction causes flank or abdominal pain, often associated with vomiting and nausea. As many as 10% of children with UPJ obstruction reportedly have hypertension.6 Severity of symptoms varies with the extent of obstruction, whether partial or complete.


In this patient, the history of left-sided, colicky abdominal pain radiating to the left inguinal region, presence of costovertebral tenderness, and blood on urinalysis initially led to consideration of a kidney or ureteric stone. The anatomic differential diagnosis for the patient also included blockage of the left sigmoid and descending colon, lower pole of the left kidney, spermatic cord, and/or ureter. However, the differential diagnosis of sudden, intense, colicky pain also includes constipation, bowel obstruction or perforation, appendicitis with impacted feces, testicular torsion, renal stone, renal obstruction, and pancreatitis.7,8


A noncontrast spiral CT scan of the abdomen and pelvis is the standard method of determining the presence and location of a calculus and the extent of proximal hydronephrosis.9


Severe increases in dilation of a hydronephrotic kidney, decreased renal function, and abdominal colic are accepted indications for surgical correction in children with UPJ obstruction.3 Surgical options include endopyelotomy with balloon disruption and stent placement, open pyeloplasty, and minimal access (laparoscopic or robotic) pyeloplasty.10 The last is a minimally invasive, safe, and effective procedure, with shorter hospital stay, excellent outcomes, and minimal additional risk of postoperative complications. The goal of surgery is relief of symptoms and renal protection.11

Treatment of newborns with a diagnosis of prenatal hydronephrosis has undergone a swing from preemptive surgical intervention to a more conservative approach.12


Left untreated, UPJ obstruction can potentially cause significant renal damage, including interstitial fibrosis, glomerular changes, medullary dysplasia, and scarring. Pyelonephritis may occur because of urinary stasis. Outcome of UPJ obstruction treatment varies by approach. Open pyeloplasty consistently achieves higher than 90% success results.13 Minimal access pyeloplasty produces results that are at least as good as those of open surgery but has the advantage of being minimally invasive, which decreases inpatient hospitalization time.14


This patient had good oral intake and was not given intravenous fluids to avoid worsening the hydronephrosis. His pain was managed with intravenous morphine. He underwent cystoscopy with placement of a left double-J ureteral stent to act as a scaffold (Figure 2). He was discharged home and will follow-up as an outpatient in the renal and urology clinics.

This case emphasizes the importance of expanding the differential beyond renal calculi to include anatomic obstruction in patients with colicky abdominal pain, flank tenderness, and hematuria.