Urology Case Studies

CHIEF COMPLAINT

This 9-1/2-year-old boy is admitted for diagnostic testing because of polyuria and hyposthenuria.

HISTORY OF PRESENT ILLNESS

He was initially referred to me by the school nurse because he needed to urinate about every 45 minutes at school.  Never has dysuria or enuresis but, according to him and the mother, he gets up about 2 or 3 times every night to void and also voids about

6 times per day.  This has been going on for years, and they deny any recent weight loss or polydipsia.

He was initially examined in October, and at that time a urine dipstick was negative for glucose and showed a specific gravity of 1.010.  The following day a first a.m. specimen was obtained, which again showed a specific gravity of 1.010.  It was decided that he needed to have a workup for possible concentrating defect either due to ADH deficiency or renal disease.  Blood work was obtained, which showed a sodium of 134, potassium 3.4, chloride 101, C02 29, uric acid 3.3, BUN 9, and creatinine 0.2.  A spun hematocrit was 36, and his blood pressure was 98/50.  Since juvenile nephronophthisis was a diagnostic possibility, an ultrasound was ordered and that showed no cysts or other pathology.  At that time he also got a double-voided a.m. urine specimen and showed specific gravity of 1.014 with an osmolality of 602, sodium of 174 mEq/L, and creatinine of 43 mg/dL.

Because of the excessive urinary sodium excretion and earlier evidence for hypokalemia, though borderline, I discussed his case with the pediatric nephrology fellow, who suggested a workup to rule out Bartter syndrome.  Consultation with pediatric endocrinologist also agreed with this and the fact that he probably does not have a complete form of diabetes insipidus since his urinary osmolality was over 500, but he could have a partial form, perhaps secondary to potassium deficiency.  Therefore, it was decided to admit him for diagnostic testing.

PAST MEDICAL HISTORY

Past medical history is essentially unremarkable.

FAMILY AND SOCIAL HISTORY

Mother has insulin-dependent diabetes, but the siblings do not have any problems with polyuria, even though they get up about once a night to void.  There is also a history of recurrent UTIs in the mother and the maternal grandfather.

REVIEW OF SYSTEMS

Remarkable for only some learning problems.  He was also referred to me earlier this year to evaluate for attention deficit disorder prior to placement in special education.  He was not started on any stimulant medication until the cause of his polyuria could be definitively diagnosed.

PHYSICAL EXAMINATION

Weight is 34.6 kg.  He is afebrile with stable vital signs.  Blood pressure 110/70.  General examination reveals this is a well-developed and well-nourished young Hispanic boy is no distress, appeared to be of normal intelligence and not very hyperactive.  Skin is normal.  No adenopathy.  HEENT is remarkable for only a slightly high-arched palate and moist mucous membranes.  Heart is without murmur.  Abdomen is soft, without tenderness or organomegaly.  Genitalia are Tanner
stage I.

PROBLEMS

1. Polyuria with hyposthenuria.

2. Rule out diabetes insipidus.

3. Rule out Bartter syndrome.

ASSESSMENT

We repeated his electrolytes on admission this morning, and he has normal potassium of 4.3, which makes Bartter syndrome unlikely, although his magnesium was borderline at 1.8.  He seems to be urinating quite a bit, about 800 cc over the first 4 hours of observation, so we will probably be doing a vasopressin test in addition to water-deprivation test and 24-hour collection for urinary electrolytes and creatinine.

PLAN

Repeat electrolytes and do plasma renin and aldosterone levels tomorrow.  Once the 24-hour urines are collected, we will make him n.p.o. and do the water-deprivation test followed by vasopressin test as outlined in the Harriet Lane handbook.  He will be discharged once these tests are completed.

FOOTNOTE

Line 11 (Page 1).  HPI was translated in the heading.

Line 48 (Page 1).  The mother is not a sibling; therefore, other was deleted.

Line 11 (Page 2).  Exam was translated in the heading.

Line 12 (Page 2).  Kilos was changed to kg (kilograms).