Case discussion ED conference 11/04/16 Jelte Kelchtermans

Case description: A 5-year-old girl presents to the ED with a 4-day history of NBNB vomiting. The patient has had several episodes of watery non bloody diarrhea over the first two days of illness but has had well formed stools of the past two days. The patient also has a 5-day history of rhinorrhea. Mother reports that over the last 24 hours the patient has been less active. No associated abdominal pain, dysuria, fever, chills, rash, cough, change in fluid intake or urine output. The patient visited the ED on day 2 of illness and was diagnosed with a probable viral Gastroenteritis and discharged after passing an oral tolerance test. No significant past medical or surgical history. No significant family history. Not currently taking any medications. No known allergies. Vaccinations are up to date. Bp 100/50 mmHg, RR 30/min, HR 140/min. The patients’ urine specific gravity is 1.004 and her blood sodium level is 146 mmol/L.

What test is most likely to reveal the underlying diagnosis? 1. Brain MRI 2. Kidney MRI 3. ADH level 4. Water deprivation test 5. Stool culture

What test is most likely to reveal the underlying diagnosis? 1. Brain MRI 2. Kidney MRI 3. ADH level 4. Water deprivation test 5. Stool culture

Diabetes insipidus Polydipsia and polyuria: Central Diabetes insipidus (most common with 3/100,000) Nephrogenic diabetes insipidus Compulsive water drinking

Central (Hypothalamic/Pituitary Lesions Leading to Insufficient Production or Release of ADH) Postoperative brain surgery Intracranial lesions (cysts, aneurysms, tumors of pituitary, brainstem) Infiltrative malignancies (lymphoma, leukemia) Infections, including encephalitis, meningitis, abscess Head trauma Hypoxic injury Congenital, inherited as an autosomal dominant disorder

Nephrogenic (Resistance to ADH due to interference with the Renal Concentrating Mechanism) Acquired metabolic aberrations Hypokalemia (chronic, Bartter syndrome) Hypercalcemia Hypercalciuria (rare) Diabetes mellitus Medullary damage Chronic pyelonephritis Infiltrative disease (leukemia, lymphoma, amyloidosis) Sickle cell disease Cystinosis Other forms of chronic renal failure Obstructive uropathy Drugs (lithium, demeclocycline, amphotericin B, diphenylhydantoin) Inherited X-linked Autosomal recessive Autosomal dominant

Pathophysiology

Presentation Poor feeding + failure to thrive due to excessive fluid consumption and blunted appetite Irritability due to hypernatremia and dehydration Nocturia due to large urine volume Constipation due to dehydration Seizures and dehydration may develop with late recognition of the disease High urine output despite dehydration

Diagnosis Blood/urine glucose (DD DM) 24 hour urine Urinary specific gravity Water deprivation test (DD severe DI vs mild DI and polydipsia) DDAVP intranasal test (DD Nephrogenic and Central DI) MRI of the brain (Loss of bright T1-weighted signal within the sella)

Management Sufficient water to maintain normal electrolytes Low renal solute load to minimize water loss If urine concentrates to 1,000 mOsm/kg of water (normal), the kidney can excrete a solute load of 300 mOsm in 300 mL of urine. However, if urine concentrates only to 100 mOsm/kg of water, excreting 300 mOsm requires 3 L of urine. Adequate calories to support growth. Pharmacotherapy (E.g Thiazide, NSAID) usually is needed.

References Diabetes Insipidus. Pablo Saborio, Gary A. Tipton, James C.M. Chan. Pediatrics in Review Apr 2000, 21 (4) 122-129; DOI: 10.1542/pir.21-4-122 Back to Basics. Michael A. Linshaw. Pediatrics in Review Oct 2007, 28 (10) 372- 380; DOI: 10.1542/pir.28-10-372 Central diabetes insipidus misdiagnosed as acute gastroenteritis in a pediatric patient. Laleh Gharahbaghian, MD et all. Canadian Journal of Emergency Medicine, 10(5), pp. 488–492. doi: 10.1017/S1481803500010642.