Embryology · Skeleton, muscles, limbs and skin
Poland sequence and prune belly syndrome !
- Malformation
Two rare muscle defects: in Poland part of the chest muscle on one side is missing; in prune belly the belly wall lacks muscle.
Updated 2026-11-01
See it in 3D: Pectoralis major · Pectoralis minor · Nipple · Rectus abdominis · External oblique · Transversus abdominis · Kidneys · Ureters · Testes
What it is
Both are defects of hypaxial muscles. In Poland sequence the sternal head of pectoralis major is missing on one side, often with a small hand and joined fingers on the same side. In prune belly syndrome the abdominal wall muscles are deficient, together with bilateral undescended testes and dilated urinary tract. Both are asked as examples of congenital muscle defects.
Embryological cause
- Poland: an interruption of blood flow in the subclavian artery or its branches around week 6, when the pectoral muscle and the hand form, is proposed.
- Poland: the defect reaches the derivatives of the same territory: pectoral muscle, breast, nipple, upper ribs and hand.
- Prune belly, obstruction theory: an early urethral obstruction distends the bladder and abdomen and the wall atrophies.
- Prune belly, mesoderm theory: a primary mesodermal defect affects the abdominal wall, urinary tract and testicular descent together.
- Oligohydramnios from the uropathy causes pulmonary hypoplasia and compression deformities.
Markers
- Subclavian artery
- Symbrachydactyly
- Megacystis
- Oligohydramnios
How it presents
- Poland: one-sided, more often right; more than twice as common in males; about 1 in 20,000.
- Poland: asymmetric chest, a higher or absent nipple, a small breast in girls and symbrachydactyly.
- Prune belly: triad of a lax, wrinkled abdominal wall, bilateral undescended testes and urinary tract dilation.
- Prune belly: almost always boys; severity depends on the kidneys and lungs.
- Prune belly: clubfoot, hip dislocation and pectus excavatum from lack of amniotic fluid.
Diagnosis
- Poland: clinical; chest CT or MRI defines muscle and ribs.
- Prune belly, prenatal: megacystis, dilated ureters and kidneys and oligohydramnios on ultrasound.
- Prune belly, at birth: renal ultrasound, voiding cystourethrogram and kidney function.
Test yourself
Think of the answer, then tap the question to see it.
Which muscle is missing in Poland sequence?
The sternal head of pectoralis major on one side, sometimes with pectoralis minor.
What is the triad of prune belly syndrome?
Deficient abdominal muscles, bilateral undescended testes and dilated urinary tract.
Which vascular mechanism is proposed for Poland sequence?
Reduced flow in the subclavian artery or its branches around week 6 of development.
Why can prune belly syndrome cause pulmonary hypoplasia?
The uropathy reduces fetal urine, causing oligohydramnios, so the lungs do not expand enough.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
- Pectoralis major
- Pectoralis minor
- Nipple
- Rectus abdominis
- External oblique
- Transversus abdominis
- Kidneys
- Ureters
- Testes
Related
- Muscles: somites, epaxial and hypaxial
- Skin, hair, nails and the mammary glands
- Limb defects: amelia, meromelia, polydactyly and syndactyly
- Cryptorchidism
- Pulmonary hypoplasia
- Amniotic fluid: polyhydramnios and oligohydramnios
- Duplicated ureter, UPJ obstruction and posterior urethral valves
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Poland syndrome: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Prune belly syndrome: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Langman's Medical Embryology, 13th ed., ch. 11: Muscular System (Wolters Kluwer, 2015).
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Representative model, for educational purposes only.