Children with ARPKD may produce large amounts of dilute (unconcentrated) urine and hence have polyuria (frequent urination) and polydipsia (excessive thirst). This is due to a concentrating defect related to small 1-2 mm fusiform dilatations of the collecting tubules and collecting ducts. Bed-wetting is not uncommon in school-age children and is due to the concentrating defect. Children with ARPKD have increased risk of dehydration with prolonged fevers, vomiting or diarrhea, and during times of insufficient oral fluids intake. On hot summer days and during sport activities water bottles are needed to prevent dehydration.
Growth may be impaired and twenty-five to thirty percent of children with ARPKD/CHF experience failure-to-thrive. The exact cause is unknown, but possible reasons include decreased food intake secondary to increased intra- abdominal pressure, reduced food absorption because of GI motility abnormalities and chronic renal insufficiency. Hypertension may occur in up to 80% of children, is often severe and can develop in the first several months after birth. There is a strong relationship between hypertension and decreased renal function, however hypertension may present with normal renal function, or hypertension may be absent with ESRD. Hypertension is a factor in the progression of renal deterioration and without aggressive treatment severe hypertension can be life-threatening. The cause of hypertension is not clearly understood; possible explanations include reduced renal blood flow, activation of the renin-angiotensin system, or abnormal blood serum sodium handling. Hyponatremia (low serum sodium level) may result from defects in free water excretion (may spontaneously correct itself). Other serum electrolytes are generally normal and metabolic acidosis is not a significant feature of the disease.
Sixty to 100% of ARPKD patients have palpably enlarged kidneys. There is no treatment at this time to decrease kidney size. The enlarged kidneys may secondarily cause inguinal and umbilical hernias. ARPKD has no clear association with vesicoureteric reflux (VUR), bladder dysfunction or other GU anomalies. There is no definitive data to suggest that UTI’s (urinary tract infection) have a higher than normal incidence in the ARPKD population. However white blood cells (pyuria) are often present in the urine without infection. Urine cultures should confirm and guide all antibiotic therapy.