Fistula and septicaemia

Milk fistula

Fistula is a complication of untreated lactational abscess, and is rare. There are less than ten cases reported in the research literature to date. Of those reporte,d they have all spontaneously resolved without active intervention while the patient continues to breastfeed.

It is a pathological connection between a lactiferous duct and the skin, which drains milk.

• There is one published case report, by Lim et al 2018, of a fistula which occurred during a second lactation after an abscess ruptured in the first lactation. In this case, resolution occurred when breastfeeding was ceased.1

• A retrospective audit by breast surgeons Johnson & Mitchell 2019, published only as an abstract, found that no fistula developed after surgical intervention for breast masses including abscess from 4 pregnant and 43 lactating patients (surgical excision of the mass, percutaneous drain insertion, stab incision and drainage, core-need biopsy, and punch biopsy).2

  • The authors state, drawing on clinical experience, that milk fistula after incision and drainage of a lactational abscess is a very rare occurrence, though this audit is too small to support their claim.

  • These authors argue that the remote risk of fistula formation is not a reason to delay incision and drainage of an abscess, and that

  • A fistula, if it occurs, typically closes quickly due to the highly vascular wound-healing environment of the lactating breast, with no reason to cease breastfeeding.3

The difference between a mammary fistula and milk fistula

A mammary fistula is different to a milk fistula and is typically mistaken as recurrent peri-areolar abscesses. Mammary fistulae typically occurs in smokers and are due to squamous metaplasia of the lactiferous ducts (SMOLD) – whereas ducts are lined by bilayer cuboidal glandular epithelium. The squamous metaplasia facilitate keratin shedding which obstructs the ducts, causing rupture, inflammation and subsequent infection. This is why a mammary fistula requires formal surgical excision, due to the pathophysiological changes that have occurred within the duct itself.3

Septicaemia

Before the advent of antibiotics, puerperal septicaemia from severe inflammation of the lactating breast was a common cause of maternal death in the post-birth period. If a lactational abscess is worsening despite oral antibiotics and other interventions, intravenous antibiotic treatment prevents or treats this catastrophic outcome.

Selected references

1. Lim GH, Ng RP. Milk fistula following puerperal breast abscess. Clinical Case Reports. 2018;6(4):773-774.

2. Johnson HM, Mitchell KB. Is milk fistula a legitimate concern or an unfounded fear? A cohort study to estimate incidence. Journal of the American College of Surgeons. 2019;229(4S1):S37.

3. Ofri A, Dona E, O'Toole S. Squamous metaplasia of lactiferous ducts (SMOLD): an under-recognised entity. BMJ Case Rep. 2020 Dec 9;13(12):e237568.