Page 463 - Medicine and Surgery

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Chapter 11: Diabetes mellitus 459

Diabetic amyotrophy present with sudden onset of andlackofreflexbradycardiaontheValsalvamaneouvre.

pain and weakness with an absent tendon jerk (usually The bladder may be palpable.
the knee). The important differential diagnosis is a
spinal or cauda equina cause of the radiculopathy. Complications
Pyelonephritis, overgrowth of bowel bacteria causing di-
Investigations arrhoea.
In most cases, this is not necessary, as the cause is
clear. Occasionally, it may be useful to exclude other Management
causes, particularly in cranial nerve palsies when a space- Treatmentdependsonthesymptomsandcomplications.
occupying lesion may be excluded with CT or MRI. Postural hypotension is treatable with fludrocortisone (a
mineralocorticoid), but this may cause hypertension to
be worse. Impotence is treatable with sildenafil.
Management
Management is as for diffuse symmetrical neuropathies.
Prognosis
Symptomatic autonomic neuropathy is associated with
Autonomic neuropathy areduced life expectancy.
Incidence
About 40% of diabetic patients have autonomic neu- Diabetic ketoacidosis (DKA)
ropathy on screening. It increases with the duration of
Definition
the disease.
The hyperglycaemic and metabolic acidotic state which
occursinTypeIdiabetesduetoexcessketoneproduction
Pathophysiology as a result of insulin deficiency.
This probably has similar pathogenesis to the diffuse,
symmetrical neuropathy. The autonomic nervous sys- Aetiology
temisinvolved, causing disturbance of functions such Precipitating factors include infection, trauma, surgery,
as postural vasoconstriction, gastrointestinal motility, burns and myocardial infarction. It is associated with
bladder emptying, sexual function (erection and ejac- poor diabetic control.
ulation). Life-threatening disturbances include reduced
awareness of hypoglycaemia and cardiorespiratory ar- Pathophysiology
rest. Sudden unexplained death is more common. Patients may omit or reduce their insulin when ill,
because they are eating less and therefore believe they
Clinical features requirelessinsulin.Infact,stressessuchasanintercur-
Postural hypotension, causing dizziness, faints and rent infection increase the secretion of glucagon and

falls. other counter-regulatory hormones which oppose in-
Nausea, vomiting and diarrhoea or constipation due sulin, so that insulin requirements increase during ill-

to abnormal gastrointestinal motility. ness.
Bladder problems include incomplete emptying, The result of this is a severe catabolic state: there is un-

chronicurinaryretentionandthispredisposestomore controlled glycolysis, lipolysis and protelolysis. This
severe urinary tract infections, such as pyelonephritis. causes hyperglycaemia and a rise in free fatty acids
Failure of erection is due to reduced parasympathetic which are the substrates for ketone body formation

activity (may also result from depression or atheroma (ketogenesis) within the liver. Normally insulin op-
in the pudendal arteries). Failure of ejaculation due to poses ketogenesis, but in conditions of insulin defi-
impaired sympathetic activity. ciency, glucagon and catecholamines increase keto-
Increased sweating. genesis. The ketone bodies produced are acetoacetic

Examination shows a >20 mmHg fall in systolic BP on acid, acetone and hydroxybutyrate which result in a
standing, loss of normal sinus arrhythmia on breathing metabolic acidosis.