Pyloric stenosis

Key points

Maternal treatment with macrolides thought to be risk factor

The risk of hypertrophic pyloric stenosis in offspring of mothers who had pyloric stenosis as a baby is greater than if the father has pyloric stenosis

Sequence of electroluyte disurbances

Vomiting - loss of HCl + fluid

Parietal cells make more HCl - creating more HCO3-, also pancreas no longer secretes HCO3-, so serum HCO3- rises = hypochloraemia + metabolic alkalosis

Renal and respiratory compensation:

Kidney wastes HCO3- making an initial alkaliuria

Mild hypoventilation, respiratory acidosis

H+/K+ exchange in distal convoluted tubule - results in hypokalaemia

Na-K+ pump + Renin-Angiotensin-Aldosterone System in kidneys activates due to loss of fluid RAAS results in loss of K+

H+ secreted as kidneys attempt to retain K+ = paradoxical aciduria

In later stages, dehydration and shock may cause lactic adcidosis

Radiology

USS (target sign) - pyloric length of >15mm and pyloric wall thickness >3mm are indicative, however an experienced Paediatric Radiologist may be able to diagnose it more specifically - may show that fluids not going through pyloric channel

UGI contrast may show elongated pylorus and can show marked delayed gastric emptying.

Also string sign, double-track sign, or beak sign

AXR is not a sensitive investigation however it may show a large stomach bubble and caterpillar signs, which are waves of peristalsis in a large stomach bubble that gives the appearance of a caterpillar

If normal USS, consider other causes such as duodenal web and perform UGI contrast

Management

Ensure adequate IV fluids with K+ supplementation until blood gas is corrected

Atropine can be used for a patient that is unfit for theatre or who has got extensive adhesions

IV atropine 6x per day prior to feeds for 1 week

PO atropine for up to 6 weeks at home

60-90% success

Operation: Open or laparoscopic pyloromyotomy

Cochrane review 2021: Laparoscopic approach may be associated with very small increased risk of perforation or incomplete myotomy, but insufficient evidence to compare other outcomes such as length of stay, incisional hernia etc.

Both methods are acceptable UK practice

Specific but rare complications are incomplete myotomy (do UGI contrast to confirm) and perforation:

If perforation noticed intra-op:

Small perforation - suture (if possible) and omental patch

Large perforation - close myotomy, rotate 90 degrees and do new one

If perforation detected post-op:

AXR with contrast, laparoscopy or laparotomy if doubt

Do not wait for child to get unwell

If confirmed, PICC line, antibiotics and antifungals

Always do contrast before restarting feeds

References

Hirschl, Ron, et al., editors. "Hypertrophic Pyloric Stenosis." Pediatric Surgery NaT, American Pediatric Surgical Association, 2020. Pediatric Surgery Library, www.pedsurglibrary.com/apsa/view/Pediatric-Surgery-NaT/829037/all/Hypertrophic_Pyloric_Stenosis.

Jacobs C, Johnson K, Khan FA, Mustafa MM. Life-threatening electrolyte abnormalities in pyloric stenosis. J Pediatr Surg Case Reports. 2019 Apr 1;43:16–8.

Amini B, Elfeky M, GHADBAN M, et al. Pyloric stenosis. Reference article, Radiopaedia.org (Accessed on 05 Jun 2024) https://doi.org/10.53347/rID-1941

Staerkle RF, Lunger F, Fink L, Sasse T, Lacher M, von Elm E, Marwan AI, Holland-Cunz S, Vuille-dit-Bille RNicolas. Open versus laparoscopic pyloromyotomy for pyloric stenosis. Cochrane Database of Systematic Reviews 2021, Issue 3. Art. No.: CD012827. DOI: 10.1002/14651858.CD012827.pub2

Shailinder Singh - Nottingham Children's Hospital Paediatric Surgery teaching