PEDIATRIC UROLOGY

Intermittent Hydronephrosis Secondary to Ureteropelvic Junction Obstruction: Clinical and Imaging Features
Tsai JD, Huang FY, Lin CC, Tsai TC, Lee HC, Sheu JC, Chang PY
Department of Pediatrics, Mackay Memorial Hospital, Taipei, Taiwan
Pediatrics. 2006; 117: 139-46

• Objective: We sought to assess the clinical and imaging findings in intermittent hydronephrosis secondary to ureteropelvic junction obstruction, with particular emphasis on the characteristic ultrasonographic findings.
• Methods: This prospective, longitudinal, observational study included all children who had intermittent ureteropelvic junction obstruction and presented with abdominal pain over 6 years. Renal ultrasound was used as an initial screening tool to detect intermittent hydronephrosis. Renal ultrasonography was repeated every 1 to 2 days to record serial changes from the symptomatic to the asymptomatic stage. Their clinical manifestations and imaging findings were studied.
• Results: Eighteen patients (14 boys, 4 girls) were studied. Most had sharp pain that began acutely and typically lasted for < 2 days. Most of the children (16 of 18) had nausea and vomiting that accompanied the pain. The acute episode generally resolved spontaneously and was followed by a pain-free interval that ranged from days to months. Factors that predisposed to an attack included increased water intake, vigorous exercise, or bladder distention. All patients had clearly demonstrable obstruction of the renal pelvis during an acute attack, a finding that diminished or resolved during the symptom-free intervals. During convalescence, all patients had renal pelvic wall thickening on ultrasonography. This finding appeared on the second or third day after a painful episode subsided, persisted for 6 to 9 days, and then disappeared in the symptom-free stage. Pyeloplasty was performed in 17 patients, none of whom had recurrent pain on follow-up. Extrinsic obstructions were found in 9 patients.
• Conclusions: The keys to diagnosis are awareness of the syndrome, a detailed history, and immediate and serial imaging studies during painful crises. A thickened renal pelvic wall during convalescence is an important ultrasonic sign of intermittent hydronephrosis.
  
  
• Editorial Comment
  The authors review their experience with intermittent hydronephrosis. This problem typically presents with severe acute, but episodic, flank pain, often associated with nausea/vomiting. The condition is rare (18 patients over 6 years), but making the diagnosis is very rewarding to the patients and their families. Surgery was needed in all cases, but none of the patients had episodic pain after repair.
  The authors point out the difficult with diagnosis and suggest frequent renal sonography, with the emphasis being on emergency ultrasound during an episode of pain, that is then compared to an ultrasound done when the patient is asymptomatic. This has been the most diagnostic test in our hands also. Diuretic renography and other provocative tests have been unreliable, whereas an ultrasound during an acute episode has been uniformly revealing.
  The authors also propose a new test; measurement of the thickness of the renal pelvic wall during the convalescence after an acute episode. The finding of increased renal pelvic wall thickness was seen in all the author’s patients between 2 and 9 days after the acute episode and then disappeared. This new finding is most helpful, as in many instances, an ultrasound of the kidney during the acute crisis may not be feasible. Further substantiation of this finding is needed, but it should be looked for in all patients with symptoms compatible with an intermittent hydronephrosis.
  The authors note that it is expected that an extrinsic lesion would be the cause of an intermittent hydronephrosis. Indeed, in their series they found this in 53% of cases. Two cases of ureteral polyps were also noted, but in the others, the actual explanation for the intermittent hydronephrosis seems to be an intrinsic abnormality at the UPJ. The pathophysiology in these cases is unclear, but the clinical scenario was convincing.
  Overall, the authors bring to light an important clinical syndrome. In addition to the usual criteria, the study proposes a novel new finding that is very exciting.

Dr. Barry A. Kogan
Chief and Professor of Urology and Pediatrics
Albany Medical College
Albany, New York, USA