case report antenatal so no graphic diagnosis of meconium

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CASE REPORTS 47 7

Clinical Radiology (1997) 52, 477-479

Case Report: Antenatal Sonographic Diagnosis of Meconium

Peritonitis and Subsequent Evolving Meconium Pseudocyst

Formation Without Peritoneal Calcification

W. T. YANG , S . S . Y. HO* and C . MET REW EL I t

Department of Diagnostic Radiology, *Department of Diagnostic Radiology and Organ Imaging and ~Department ofDiagnostic Radiology and Organ Imaging, Chinese University of Hong Kong Prince of Wales Hospital, Shatin, Hong

Kong

A case of g iant meconium pseudocyst secondary to rupture

from in tes t inal obstruct ion d iagnosed by in utero sonogra-

phy is presented_ The diagnosis of intestinal obstruction was

made in the late second t r imester before development of

polyhydramnois , and the d iagnosis of meconium cyst made

in the th ird t r imester despi te the abse nce of in tra-abdom inal

calcif icat ion . Exploratory laparotomy immediately after

b ir th revealed a g iant pseudocyst at the s i te of rupture

immediately proximal to d is tal i leal at res ia with associated

in utero volvulus .

Conventional radiographic features of meconium peri to-

ni t is with secondary meconium cyst formation are well

described [1- 6]. With the advent of h igh resolut ion real

t ime ul t rasound (US), the special ro le of sonography in

detect ing congenital malformations in utero has been es tab-

l ished. We p resent a case in which sonographic d iagnosis of

in test inal obstruct ion was m ade at 27 weeks gestat ion before

the developmen t of polyhydram nois , and a sonographic

d iagnos i s o f mecon ium pseudocys t was made a t 36 weeks

gestat ion despi te the absence of in tra-abdominal

calcification.

Laparotomy at 10 h of life conf irmed ileal atresia wi th associated volvulus

and a large pseudocyst at the rupture site in the distil ileum. Small bowel

resection and anastomosis were performed after 500 ml of greenish brown

fluid were drained fi'om the pseudocyst. Patholog y of the resecte d small

bowel spec imen did not reveal a ny calcification intraluminally or on the

serosal surface. The baby recovere d well postoperati vely and has achieved

normal developmental milestones. Subsequently, a sweat test was normal.

Discussion

The incidence of congenital small bo wel atres ia is 0.38 in

10 000 newborn s [7] and the preva lence of neonatal me co-

nium peritonitis is estimated at one in 30 000 live births [8].

On sonography, fetal bowel obstruct ion characteris t ical ly

consis ts of d i lated sonolucent masses occupying the fetal

abdominal cavi ty asymmetrical ly , with associated polyhy-

dramnois [7]. The differential diagnosis includes a dis-

tended urinary b ladder, usual ly in the middle of the lower

abdomen, and mesenteric and ovarian cysts , usual ly located

to one s ide of the abd ominal cavi ty . Dilated loops f i l l ing the

abdominal c avi ty suggest obstruct ion of the small bowel .

Case Report

A 31-year-old Chinese gravida 2 para I with an uneventful previous

pregnancy and delivery, who was visiting Hong Kong presented to the

antenatal US scree ning clinic at 27 weeks gestati on for fetal anoma ly

screening. A n isolated markedly dilated b owel loop was see n in the mid-

abdomen of the fetus without associated ascites or polyhydra mnois (Fig. 1).

The rest of the examination was normal. The diagnosis was small bowel

obstructi on seconda ry to either ileal atresia, me conium ileus or small bowel

volvulus, wi th a high risk of intestinal perforation. A follow-up US at 29

weeks gestation sh owe d significant increase in size of the dilated segme nt

of bowel, with associated ascites and polyhydranmois (Fig. 2). The

diagnosis at this time was probable intestinal rupture and meco niumperitonitis. The third follow-up US at 36 week s gestation sho wed a large

cystic collection in the abdomen with well defined echogenic walls (Fig. 3),

which was separate from the bowel loops and mos t likely represented a

meco nium pseudocys t. An active 3400 g male infant was delive red at 38

weeks gestation by elective caesari an section. Physical examina tion

revealed gro ss abdominal distension, more significant on the fight The

abdominal wall was intact and anus patent. Both testes were descende d

without associa ted scrotal swe lling or inguinal herniae_ Abdomin al radio-

graphs at 5 h o f life showed a large soft tissue mass occupying the right

hemiabdomen causing displacement of bowel loops to the left_ There w as

no radiograplucally demonstra table calcification (Fig. 4). US demonstrated

a predominantly right sided cystic abdominal mass with well circ umscribed

echogenic walls filled with echogenic viscid content and a solitary echo-

genic focus with poster ior acoustic sha dowing within (Fig. 5). There was no

sonogra phicall y visible calcification of the periphery or rim. The hepato-

biliary system, adrenals and kidneys were normal. The most likely

diagnosis was a mec onium pseudocyst secondary to in utero bowel rupture.

Corres pondenc e to: Dr W.T. Yang, Department of Radiology, Prince of

Wales Hospital, Shatin, NT, Hong Kong.

© 1997 The Royal College of Radiologists,Clinical Radiology, 52, 477 479.

Fig. 1 - Transverse scan of the fetal abdomen at 27 weeks gestation shows

an isolated markedly dilated small bowel loop (arrowheads). No ascites or

polyhydrarnnois is present.



CASE REPORTS 4 79

the third antenatal ul t rasound was performed soon after the

deve lopm ent of the pseud ocys t and before ca lc i f ica t ion had

been deposi ted in sufficient quant i ty to be vis ible radio-

graphical ly or echographical ly. Although calcif icat ion may

develop within days his tological ly, radiographic and sono-

graphic eviden ce of calcif icat ion usual ly requires weeks

[4,21].

In conc lus ion , the d iagnos i s of mecon ium pseudo-

cyst should be considered in the set t ing of fetal bowe lobstruct ion with sequent ial polydramnois , asci tes and

cys t format ion , even in the absence of in t ra -abdomina l

calcification.

Fig . 5 - Transver se abdominal u l t rasound scan a t 5 h of l i fe shows a large

cyst ic wel l c i rcumscribed mas s wi th echogenic wal ls and echogenic content

but no demonst rab le ca lc i f ica t ion peripheral ly or in t raperi toneal ly . The

sol i tary echogenic focus wi th in the cyst (arrow) represents in t racyst ic

meco nium calc i f ica t ion , a l so seen in Fig . 3 .

Less than 10 cases of prena ta l ly d iagnosed m econium

peri toni t is have been reported in the l i terature [14-20]. The

sonographic d iagnos is of meconiu m per i toni t is should be

considered in the presence of a fetal intra-abdominal hyper-

echoic mass , part icularly i f associated with asci tes and

polyhydramnois . I so la ted asc i t es may occas iona l ly be the

only f inding. W hen asci tes develop s suddenly in a fetus with

bowel obstruct ion, as in our pat ient , the diagnosis of

meconium peri toni t is should be s t rongly suspected.The sonographic fea tures of a meconium cys t a re a

thickened, wel l c i rcumscribed, echo genic cys t wal l with

areas of focal calcif icat ion and echogenic viscous content

[8] . Calcif icat ion o f mecon ium peri toni t is is usual ly l inear in

appearance as opposed to in t ra lumina l me conium ca lci f ica -

t ion which appears as punctate echogenic foci in the bowel

lumen, as seen in our patient (Figs 3 & 5) [8]. Peritoneal

calcif icat ion is the most common and characteris t ic f inding

of meconium per itoni ti s on both prena ta l sonography and

postnatal radiography [8] . The different ial of a large intra-

peri toneal bowel related cys t ic mass with echogenic content

includes a dupl icat ion cys t , which was unl ikely in view of

our init ia l f inding of bow el obstruct ion. Other non u rinary or

bowel related cys t ic masses in the fetal abdomen which

enter the different ial l is t include an haemorrhagic ovarian

cyst , mesenteric and omental cys ts (usual ly lymphangio-

mas) and choledochal cys ts (usual ly in the f ight upper

quadrant) [8] . Awaren ess of the s i te , prevalence and usual

sonographic appearances he lp sugges t the mos t l ike ly

diagnosis . Despi te the absence of calcif icat ion in the cys t

wal l , peri toneum or scrotal sac in our pat ient , the prenatal

d iagnos i s of a meconium cys t was made because of the

evolut ion of abnormali t ies on fol low-up. I t i s poss ible that

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© 1997 The Royal College of Radiologists, Clinical Radmlogy, 52, 477-479.

case report antenatal so no graphic diagnosis of meconium

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