Congenital chloride diarrhea (CCD) is a lifelong condition that causes large, watery stools (diarrhea) that contain an excess of chloride. Those with CCD have diarrhea even before birth. Signs of CCD before birth may be detected with an ultrasound, and may include an increased amount of amniotic fluid (polyhydramnios) and enlarged (dilated) intestinal loops in the fetus. Newborns with CCD are often premature and may have a swollen-looking abdomen (abdominal distention). For this reason, CCD is sometimes first mistaken for an intestinal obstruction. CCD causes electrolyte imbalances including low blood sodium levels (hyponatremia) and chloride levels (hypochloremia). Electrolyte imbalances and severe dehydration can lead to volume depletion (too little fluid surrounding body cells), loss of acid from the blood (metabolic alkalosis), hyperaldosteronism, delayed growth and development, and kidney damage (nephropathy). Untreated CCD can ultimately be fatal within the first weeks or months of life.

CCD is caused by mutations in the SLC26A3 gene and inheritance is autosomal recessive. The diagnosis is based on detecting excessive chloride in the feces, when the newborn is in fluid and electrolyte balance.

Treatment aims to control symptoms by replacing lost electrolytes and water, and typically involves oral or intravenous sodium chloride and potassium chloride. Infants who are diagnosed and treated very shortly after birth have the potential to grow and develop normally. If not treated adequately, CCD ultimately causes chronic kidney disease.

Congenital chloride diarrhea (CCD) is a lifelong disease, so treatment focuses on managing symptoms and preventing complications. Early diagnosis and treatment in the absence of major complications can lead to normal growth and development. The main treatment is called salt substitution therapy (receiving sodium chloride and potassium chloride). Newborns are first given this therapy intravenously (by IV) and are later transitioned to oral therapy. Diarrhea will persist through therapy even when there is adequate salt substitution, although the relative amount of stool generally decreases with age.

Treatment for episodes of acute gastroenteritis ("stomach flu") in children with CCD is extremely important because they can experience rapid dehydration and loss of potassium (hypokalemia). These episodes should be treated with IV replacement of fluids and electrolytes. In adulthood, people with CCD are usually able to avoid dehydration by taking extra salt substitution.