To the Editor.—
In the QUESTION AND ANSWER section1 of the Sept 7, 1984, issue of The Journal, the evaluation of recurrent vomiting in a child is discussed.When evaluating a child for recurrent vomiting, careful consideration should also be given to the possibility of intermittent hydronephrosis. A child with partial ureteral pelvic junction obstruction can produce hydronephrosis sufficient to cause vomiting that then resolves with dehydration. Examination while in the hospital often shows a normal collecting system bilaterally. A diuretic challenge of this collecting system is sometimes necessary to detect the inadequacy of the ureteral pelvic junction.