Health Q&A: a severe chest infection and diabetes insipidus

Dr David Roche / 24 September 2012

Dr David Roche explains how a chest infection can turn very nasty and why diabetes insipidus isn’t to blame for weight gain

Chest infection

My wife was diagnosed with what the doctor called ‘shock lung’ after a severe chest infection. She is now home from hospital and is getting better slowly. Will she recover completely and how long will it take?

Shock lung is known in medical circles as acute respiratory distress syndrome. It is a serious condition with a high mortality so I am pleased to hear that your wife is now home and slowly recovering. The syndrome is the result of severe damage to the lung through many possible causes, for example infection, trauma or burns. Of these, infections are the commonest trigger, as in your wife’s case.

Instead of reacting normally to infection the whole of the lung becomes swollen, with fluid collecting in the lung tissues and in the airways. It occurs quickly and is immediately life-threatening as oxygen can no longer be transferred into the bloodstream. Artificial ventilators are used to keep the lungs working when the patient can no longer breathe efficiently for themselves.

Many patients recover very well as long as they survive the initial dangerous phase. Long-term lung damage often occurs but it is relatively mild and patients can usually manage well. The process of recovery will be slow and lengthy, however.

Diabetes insipidus and weight gain

My daughter was diagnosed with diabetes insipidus 18 months ago and is receiving treatment, but she’s finding it almost impossible to lose her excess weight. Is this because of her illness?

Diabetes insipidus is a rare condition and although it shares a name with the commoner diabetes mellitus, the two have very different causes. They share a name because the main symptom of both is the excess production of urine, but that and thirst are the only features they have in common.

Diabetes insipidus is the result of the inability of the kidneys to retain water. Normally a hormone manufactured in a part of the brain called the hypothalamus and released through the pituitary gland encourages the kidney to retain water. It is called anti-diuretic hormone (ADH or vasopressin) and if production fails the symptoms of diabetes insipidus quickly appear. There is a rarer form of the disease where ADH is produced normally but the kidneys fail to respond to it.

Some serious infections, surgery and head injury can trigger diabetes insipidus, but many cases have no known cause. ADH can be administered in tablets or a nasal spray and usually brings the disease under good control. It is unlikely that your daughter’s weight is related to this condition but to some extent that depends on what is the underlying cause of the diabetes insipidus, if there is one. If weight gain was the result of inactivity through illness as often happens, she may have to lose the excess through the usual difficult methods.

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