Describe red degeneration of fibroid — its aetiology, clinical features and management.

Definition

Red (carneous) degeneration is an aseptic necrobiosis of a large fibroid, occurring characteristically in the second half of pregnancy and the puerperium. The cause is thought to be vascular (interference with the blood supply of a rapidly-growing fibroid).

Pathology

The cut surface has a "raw-beef" (red) appearance with a fishy odour (from fatty acids), the colour being due to haemolysed red cells and haemoglobin; microscopy shows necrosis with thrombosed vessels. Partial recovery is possible — hence the term necrobiosis.

Clinical Features

In a pregnant woman — acute localised abdominal pain with tenderness over the fibroid, mild fever, vomiting and a moderate leucocytosis; it is an important cause of acute abdomen in pregnancy.

Management

• Conservative — it is self-limiting; treat with rest, analgesics and reassurance.
• Surgery is avoided in pregnancy unless complications (e.g. Torsion) supervene.

Differential Diagnosis

Other causes of acute abdomen in pregnancy must be considered — torsion of a pedunculated fibroid or ovarian cyst, acute appendicitis, abruptio placentae, ureteric colic and accidental haemorrhage; the localised tenderness over a known fibroid and the absence of peritonism point to red degeneration.

Incidence

It complicates about 5–10% of fibroids in pregnancy, typically in the second or early third trimester when a fibroid outgrows its blood supply.

Investigations

Mainly clinical; ultrasound may show a fibroid with mixed echogenicity/cystic change, with a mild leucocytosis and low-grade fever. Other causes of an acute abdomen in pregnancy must be excluded.

Course and Prognosis

It is self-limiting — the pain settles over 3–7 days with conservative care and the prognosis is good; myomectomy is avoided in pregnancy owing to the risk of severe haemorrhage.

A Note on WHY Red Degeneration Happens in Pregnancy

A useful concept is understanding why this particular degeneration is characteristically a complication of pregnancy. A fibroid depends on its blood supply, which enters chiefly from its periphery. In pregnancy, two things happen at once. The fibroid, being oestrogen-dependent, is stimulated by the high oestrogen levels and grows rapidly — but its blood supply does not keep pace with its increased bulk, so the centre of the tumour outgrows its perfusion and becomes ischaemic. At the same time, the enlarging uterus may stretch or kink the vessels supplying it. The result is infarction with haemorrhage into the substance of the fibroid — which turns it red and gives it the characteristic raw-beef appearance and fishy odour on section. Clinically this presents in the second trimester as acute, severe, localised abdominal pain with marked tenderness over the fibroid, low-grade fever, vomiting and a mild leucocytosis — a picture that mimics appendicitis, torsion and abruption. The crucial management point is that, alarming as it appears, it is self-limiting: the treatment is conservative — rest, analgesia and reassurance — and surgery must be avoided in pregnancy, since myomectomy on a gravid uterus risks torrential haemorrhage.

Occurs typically in the second trimester; managed conservatively.

• Red (carneous) degeneration: infarction with haemorrhage into a fibroid — characteristically in the second trimester of pregnancy.
• Cause: the fibroid grows rapidly under oestrogen stimulation and outgrows its blood supply → ischaemia and haemorrhage (raw-beef appearance, fishy odour).
• Presents with acute severe localised abdominal pain, marked tenderness over the fibroid, low-grade fever, vomiting and mild leucocytosis.
• Differential diagnosis: appendicitis, ovarian torsion, abruption, pyelonephritis.
• Management is conservative and the condition is self-limiting — rest, analgesia and reassurance; avoid surgery in pregnancy (risk of torrential haemorrhage).