Index of Suspicion. Case 2. Nephrogenic Diabetes Insipidus
| Title: | Index of Suspicion. Case 2. Nephrogenic Diabetes Insipidus |
|---|---|
| Author: | Mazur, DO, Britta |
| Publisher: | Pediatrics in Review |
| Date Published: | May 01, 1994 |
| Reference Number: | 105 |
N/A
Case 2 Presentation
An 11-month-old boy is evaluated in your office for psychomotor developmental delay and failure to gain weight. He was born following a full-term uncomplicated pregnancy, weighing 8 lb 3 oz and measuring 21 in at birth. He cries excessively and is never satisfied with additional milk. He has been brought in frequently for fever and vomiting, and occasionally for constipation. At 7 months of age he was diagnosed by a pediatric neurologist as having benign congenital hypotonia. At 8 months of age he was sent to the pediatric emergency department for fever, dehydration, and constipation. There was no evidence of infection, and he was treated successfully with intravenous fluids.
Physical examination reveals a mildly hypotonic infant who has right-sided hemihyperplasia. He weighs 17 lb 10 oz (below the 5th percentile) and is 28 1/4 in long (10th percentile). His head circumference is 17 7/8 in (25th percentile). His vital signs are normal and he has no visceromegaly. No dysmorphic features are noted other than his body asymmetry.
His serum sodium level is 158 mEq/L; chloride, 130 mEq/L; carbon dioxide, 24 mEq/L; blood urea nitrogen, 19 mg/dL; creatinine, 0.6 mg/dL; calcium, 9.7 mg/dL; and phosphorous, 6.3 mg/dL. Serum osmolality is 316 mOsm/L, urine specific gravity 1.005, and urine pH 5.5.
Case 2 Discussion
Diagnosis: Nephrogenic Diabetes Insipidus
The clinical picture of a male infant who has unexplained fever, failure to gain weight, and constipation associated with high levels of serum sodium and chloride and the inability to excrete concentrated urine should alert the clinician to the possibility of nephrogenic diabetes insipidus (DI).
This disorder may be difficult to identify in the first few months of life because of the nonspecific nature of the symptoms in the early stages. Polyuria frequently is absent in infancy, presumably due to the development of dehydration, hypovolemia, and a reduced glomerular filtration rate. Failure to thrive usually is the most obvious clinical finding. These infants are irritable and cry constantly. They suck eagerly, but frequently vomit unless prefed with water. A history of constipation and erratic intermittent fevers nearly always can be elicited. The fever presumably is due to dehydration.
Nephrogenic DI can be familial or acquired and is characterized by renal insensitivity to arginine vasopressin (antidiuretic hormone). Ordinarily, serum osmolality is kept constant at 285 to 295 mOsm/L by way of osmoreceptors in the hypothalamus. An increase in serum osmolality of as little as 2% will cause a response in the osmoreceptors, followed by vasopressin release. Because vasopressin causes reabsorption of water in the kidney, urine osmolality should increase. If the kidney is unresponsive to vasopressin, the patient's serum osmolality will be increased and his or her low urine osmolality inappropriately decreased. These children have normal blood urea nitrogen and serum creatinine levels, but the renal defect is demonstrated by the production of dilute urine in the face of elevated serum osmolality. Nephrogenic DI is distinguished from pituitary DI by a lack of response to exogenous vasopressin and by the appropriate rise of serum levels of arginine vasopressin in response to elevated serum osmolality. This infant had an elevated plasma arginine vasopressin level in response to his high serum osmolality, but was putting out urine with a specific gravity of 1.005.
Familial nephrogenic DI is an X-linked disorder that has variable degrees of expression in heterozygous females. When recognition of this condition is delayed, bouts of severe hypertonic dehydration may be complicated by seizures and even death.
Acquired nephrogenic DI usually is due to drugs such as demethylchlortetracycline and lithium (usually reversible) as well as fluorocarbon anesthetics, which may cause renal tubular necrosis.
The differential diagnosis of hypotonia is quite large, but a good history, physical examination, and simple laboratory evaluation will narrow the diagnostic search. Although hypotonia is not commonly described in cases of nephrogenic DI, it has been reported in at least two other patients who had the familial form.
There is no specific treatment for nephrogenic DI. Adequate hydration is essential to prevent the damaging effects of hypernatremia and circulatory collapse. Oral hydration usually is sufficient, but infants may require parenteral supplementation at times. The diet should be restricted in salt and protein because both sodium and urea enhance obligatory water secretion.
This child also had the unusual finding of hemihyperplasia (hemihypertrophy). Conditions associated with hemihyperplasia, such as Beckwith-Wiedemann syndrome and neurofibromatosis, were excluded in this infant. The etiology and pathogenesis of hemihyperplasia are poorly understood; most cases are sporadic, with a right-sided predominance of approximately 2:1. To date there are no other reported cases of hemihyperplasia associated with nephrogenic DI; the hemihyperplasia in this case seems to be coincidental. Patients whose hemihyperplasia is isolated and nonsyndromic should be screened regularly with ultrasonography for the presence of tumors, especially Wilms tumor, because neoplastic abnormalities of the kidney have been associated with hemihyperplasia.
An 11-month-old boy is evaluated in your office for psychomotor developmental delay and failure to gain weight. He was born following a full-term uncomplicated pregnancy, weighing 8 lb 3 oz and measuring 21 in at birth. He cries excessively and is never satisfied with additional milk. He has been brought in frequently for fever and vomiting, and occasionally for constipation. At 7 months of age he was diagnosed by a pediatric neurologist as having benign congenital hypotonia. At 8 months of age he was sent to the pediatric emergency department for fever, dehydration, and constipation. There was no evidence of infection, and he was treated successfully with intravenous fluids.
Physical examination reveals a mildly hypotonic infant who has right-sided hemihyperplasia. He weighs 17 lb 10 oz (below the 5th percentile) and is 28 1/4 in long (10th percentile). His head circumference is 17 7/8 in (25th percentile). His vital signs are normal and he has no visceromegaly. No dysmorphic features are noted other than his body asymmetry.
His serum sodium level is 158 mEq/L; chloride, 130 mEq/L; carbon dioxide, 24 mEq/L; blood urea nitrogen, 19 mg/dL; creatinine, 0.6 mg/dL; calcium, 9.7 mg/dL; and phosphorous, 6.3 mg/dL. Serum osmolality is 316 mOsm/L, urine specific gravity 1.005, and urine pH 5.5.
Case 2 Discussion
Diagnosis: Nephrogenic Diabetes Insipidus
The clinical picture of a male infant who has unexplained fever, failure to gain weight, and constipation associated with high levels of serum sodium and chloride and the inability to excrete concentrated urine should alert the clinician to the possibility of nephrogenic diabetes insipidus (DI).
This disorder may be difficult to identify in the first few months of life because of the nonspecific nature of the symptoms in the early stages. Polyuria frequently is absent in infancy, presumably due to the development of dehydration, hypovolemia, and a reduced glomerular filtration rate. Failure to thrive usually is the most obvious clinical finding. These infants are irritable and cry constantly. They suck eagerly, but frequently vomit unless prefed with water. A history of constipation and erratic intermittent fevers nearly always can be elicited. The fever presumably is due to dehydration.
Nephrogenic DI can be familial or acquired and is characterized by renal insensitivity to arginine vasopressin (antidiuretic hormone). Ordinarily, serum osmolality is kept constant at 285 to 295 mOsm/L by way of osmoreceptors in the hypothalamus. An increase in serum osmolality of as little as 2% will cause a response in the osmoreceptors, followed by vasopressin release. Because vasopressin causes reabsorption of water in the kidney, urine osmolality should increase. If the kidney is unresponsive to vasopressin, the patient's serum osmolality will be increased and his or her low urine osmolality inappropriately decreased. These children have normal blood urea nitrogen and serum creatinine levels, but the renal defect is demonstrated by the production of dilute urine in the face of elevated serum osmolality. Nephrogenic DI is distinguished from pituitary DI by a lack of response to exogenous vasopressin and by the appropriate rise of serum levels of arginine vasopressin in response to elevated serum osmolality. This infant had an elevated plasma arginine vasopressin level in response to his high serum osmolality, but was putting out urine with a specific gravity of 1.005.
Familial nephrogenic DI is an X-linked disorder that has variable degrees of expression in heterozygous females. When recognition of this condition is delayed, bouts of severe hypertonic dehydration may be complicated by seizures and even death.
Acquired nephrogenic DI usually is due to drugs such as demethylchlortetracycline and lithium (usually reversible) as well as fluorocarbon anesthetics, which may cause renal tubular necrosis.
The differential diagnosis of hypotonia is quite large, but a good history, physical examination, and simple laboratory evaluation will narrow the diagnostic search. Although hypotonia is not commonly described in cases of nephrogenic DI, it has been reported in at least two other patients who had the familial form.
There is no specific treatment for nephrogenic DI. Adequate hydration is essential to prevent the damaging effects of hypernatremia and circulatory collapse. Oral hydration usually is sufficient, but infants may require parenteral supplementation at times. The diet should be restricted in salt and protein because both sodium and urea enhance obligatory water secretion.
This child also had the unusual finding of hemihyperplasia (hemihypertrophy). Conditions associated with hemihyperplasia, such as Beckwith-Wiedemann syndrome and neurofibromatosis, were excluded in this infant. The etiology and pathogenesis of hemihyperplasia are poorly understood; most cases are sporadic, with a right-sided predominance of approximately 2:1. To date there are no other reported cases of hemihyperplasia associated with nephrogenic DI; the hemihyperplasia in this case seems to be coincidental. Patients whose hemihyperplasia is isolated and nonsyndromic should be screened regularly with ultrasonography for the presence of tumors, especially Wilms tumor, because neoplastic abnormalities of the kidney have been associated with hemihyperplasia.
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Winthrop-University Hospital, Mineola, NY (Britta Mazur, DO) May 1994 Address correspondence and reprint requests to Pediatrics in Review, American Academy of Pediatrics, 141 Northwest Point Blvd, P.O. Box 927, Elk Grove Village, IL 60009-0927 |
This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)
NDI can either be congenital or acquired, and is characterized by the kidneys' failure to respond to the antidiuretic hormone's message to the kidney to save some water for the body's needs. Instead of saving water, the kidney channels it out through the bladder, resulting in characteristically frequent urination and dehydration. Congenital NDI is an x-linked disorder which means it is expressed fully only in males. It is important that this form of NDI be recognized early to prevent severe dehydration and other serious complications. Acquired NDI is usually due to exposure to drugs such as demethylchlortetracycline and lithium as well as fluorocarbon anesthetics.
There is no specific treatment for NDI. The patient must always have a high enough liquid intake to avoid dehydration and its consequent damages. His diet must be restricted in salt and protein because both increase water secretion.