Ultrasonography in diagnosis of necrotizing enterocolitis

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necrotizing enterocolitis, serial abdominal X-rays were made, as per the institution protocol, all with negative findings. On the 20th day, the patient was submitted ...
case report

Ultrasonography in diagnosis of necrotizing enterocolitis Ultrassonografia no diagnóstico de enterocolite necrosante Frederico Celestino Miranda1, Yoshino Tamaki Sameshima2, Alice D’ Agostini Deutsch3, Arno Norberto Warth4,  Miguel Jose Francisco Neto5, Marcelo Buarque de Gusmão Funari6

ABSTRACT Necrotizing enterocolitis is one of the most frequent gastrointestinal emergencies in neonates, and it is generally detected clinically and radiographically. Early diagnosis is fundamental in order to limit morbidity and mortality. At the beginning of the disease, classical findings, such as abdominal distension and intestinal pneumatosis may not be detectable by conventional radiographs. In these cases, ultrasonography may help in early diagnosis. It is presented a case of necrotizing enterocolitis in a preterm newborn whose diagnosis was only possible via ultrasonography. Keywords: Enterocolitis, necrotizing/diagnosis; Enterocolitis, necrotizing/ ultrasonography; Enterocolitis, necrotizing/radiography; Infant, newborn; Case reports

RESUMO A enterocolite necrosante é uma das emergências gastrintestinais mais frequentes em neonatos, geralmente detectada clinicamente e radiograficamente. O diagnóstico precoce é fundamental para limitar a morbidade e a mortalidade. No início da doença, os achados clássicos como distensão abdominal e pneumatose intestinal podem não ser detectáveis à radiografia convencional. Nestes casos, a ultrassonografia pode auxiliar no diagnóstico precoce. Apresenta-se um caso de enterocolite necrosante em um recém-nascido pré-termo, cujo diagnóstico só foi possível pela ultrassonografia. Descritores: Enterocolite necrosante/diagnóstico; Enterocolite necrosante/ultra-sonografia; Enterocolite necrosante/radiografia; Recém-nascido; Relatos de casos

INTRODUCTION Necrotizing enterocolitis is one of the most frequent gastrointestinal emergencies in newborns, with a 10%

incidence in neonates that weight less than 1,500 g(1). Currently, there has been an increase in incidence due to increased survival of low-weight infants(2). It is believed to be secondary to multiple factors, including prematurity(3). Early diagnosis is fundamental in order to limit morbidity and mortality. Ultrasonography is not routinely used, but can be of help in early diagnosis, evidencing findings non-detectable by plain film, such as in the case reported.

CASE REPORT An extremely preterm female newborn (gestational age of 23 weeks), delivered vaginally, with extremely low weight (550 g) and Apgar of 8 to 9 minutes. On the second day of life, abdominal distension was observed that evolved with a worsening of the clinical picture up to the ninth day. Due to the clinical suspicion of necrotizing enterocolitis, serial abdominal X-rays were made, as per the institution protocol, all with negative findings. On the 20th day, the patient was submitted to ultrasonography since she was in anuria and a palpable “mass” was detected in the right flank by the pediatrician. The ultrasound showed minute sparse hyperechoic foci in the liver and interior of the portal branches consistent with aeroportia (Figures 1 and 2), as well as parietal thickening of the intestinal loops adjacent to the right flank (Figure 3); an intestinal segment was observed in this position presenting a parietal hyperechogenic ring, representing intestinal pneumatosis (Figures 4 and 5). It was also observed the presence of thick fluid in the retroperitoneal space, suggesting retroperitoneal

Study carried out at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil 1

Post-graduated course in Tomography and Magnetic Resonance of Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

2

MD Radiologist of the Ultrasonography Sector at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

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PhD; MD Neonatologist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

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MD Neonatologist of the Neonatal Unit at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

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PhD; MD Radiologista at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

6

PhD; MD Radiologist at Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil.

Corresponding author: Yoshino Tamaki Sameshima – Avenida Lavandisca, 538 – apto. 161 – Moema – CEP 04515-011 – São Paulo (SP), Brasil – Tel.: 11 3747-0433 – e-mail: [email protected] Received on: Mar 7, 2008 – Accepted on: Oct 22, 2008 einstein. 2009; 7(1 Pt 1):91-5

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Miranda FC, Sameshima YT, Deutsch ADA, Warth AN, Francisco Neto MJ, Funari MBG

Figure 1. Sparse hyperechoic foci in the liver consistent with aeroportia

Figure 4. Parietal hyperechogenic ring consistent with intestinal pneumatosis

Figure 2. Hyperechoic foci in the interior of the portal branches

A

B Figure 3. Parietal thickening of the intestinal loop adjacent to the right flank, palpable upon physical examination

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Figure 5. Reduced intestinal pneumatosis. (5A) Transversal slice; (5B) longitudinal slice

Ultrasonography in diagnosis of necrotizing enterocolitis

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perforation of an intestinal loop and anechogenic fluid in the peritoneal cavity (Figures 6 and 7). The kidneys were hyperechogenic, suggesting acute parenchymatous nephropathy. Therefore, a plain film of the abdomen was performed, which confirmed the finding of intestinal pneumatosis. As a result of these findings, the patient’s diet was suspended (maternal milk), and the patient was maintained in a fasting state for 15 days with initiation of antibiotic treatment. No surgical approach was necessary. The newborn began to urinate again 24 hours after the onset of antibiotic use and showed progressive clinical improvement. In the follow-up ultrasound tests, carried out on the 29th and 48th days of life, disappearance of the signs of intestinal pneumatosis was noted (Figure 8), as well as reabsorption of the thick retroperitoneal fluid and intraperitoneal anechoic fluid (Figures 9 and 10). The neonate showed improvement of the clinical and radiological status, and was discharged from the hospital at 109 days of life.

Figure 8. Follow-up control examination, showing thin intestinal wall and no signs of pneumatosis. Patient was re-fed 

Figure 6. Thick fluid in the retroperitoneal space, and anechogenic fluid in the intraperitoneal cavity. Hyperechogenic renal parenchyma

Figure 9. Follow-up control examination showing absence of intra- and retroperitoneal fluid

Figure 7. Thick retroperitoneal fluid

Figure 10. Follow-up control examination, showing absence of retroperitoneal fluid

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Miranda FC, Sameshima YT, Deutsch ADA, Warth AN, Francisco Neto MJ, Funari MBG

DISCUSSION Necrotizing enterocolitis affects 10% of neonates under 1,500 g of weight(1). The incidence is inversely proportional to the gestational age. Children born at 28 weeks or less of gestational age and those with extremely low weight at birth (less than 1,000 g) are at greater risk. There has been an increase in incidence due to the increased survival of low-weight infants(2). Its etiology and pathogeny remain controversial. It is believed to be secondary to multiple factors, including prematurity, that result in damage to the mucosa, intestinal ischemia and necrosis(3). Mucosal lesion may be due to infection, intraluminal content, immature immunity, release of vasoconstrictors and inflammatory mediators. The loss of mucosal integrity allows passage of bacteria and their toxins into the systemic circulation, causing sepsis in the severe forms. The bacteria penetrate the intestinal wall and the products of their metabolism lead to formation of intramural gas(1). Involvement may be diffuse and contiguous or intermittent. The most frequently involved locations are the distal ileum and proximal colon, but any portion of the bowels may be affected(2). Newborns have greater risk of developing the disease due to immaturity of some body functions, such as gastrointestinal motility, digestive capacity, circulatory regulation, intestinal barrier function, and immune defense. It manifests most commonly during the first or second weeks of life. Its clinical presentation may be indistinguishable from neonatal sepsis. Symptoms include food intolerance, delayed gastric emptying, lethargy, apnea, respiratory difficulty, arterial pressure and temperature instability, vomiting, diarrhea, and blood in the stools(3). Signs include abdominal distension, abdominal wall erythema and edema. Neonates with severe disease may experience shock. Intestinal perforation occurs in 12 to 31% of cases. Perforation increased the rate of mortality from 30 to 64%(4). Mortality is roughly 20 to 40% and is greater in neonates with extremely low birth weight(1,3). Benign cases may merely reveal abdominal signs, such as food intolerance and abdominal distension. In the present case, the clinical and radiological manifestations suggested, but did not confirm, a more severe picture. However, since the result of the ultrasound test demonstrated signs of intestinal loop distress with blocked perforation, the choice was made to keep the infant in a fasting state with parenteral nutritional support for 15 days, with no surgical treatment and she progressed to cure. Plain film is the modality of choice in cases of suspected necrotizing enterocolitis. The follow-up protocol depends on severity of the disease and may einstein. 2009; 7(1 Pt 1):91-5

vary from 6 to 24 hours. It should include abdominal radiographs with vertical and horizontal rays and with the patient in a supine position, to assess the presence, quantity, and distribution of gases, including intramural intestinal gas, intraluminal gas, gas in the portal system, and free intraperitoneal gas. Non-specific signs include diffuse distension and asymmetric pattern of intestinal gases. Specific signs include intestinal pneumatosis (intramural air) and gas in the portal system(5). Pneumatosis may have a linear appearance when intramural air is subserous or a bullous appearance when the air is submucosal(6). Intramural submucous gas may be mistaken for feces, but radiological detection of feces in the colon is rare in premature infants less than two weeks postnatal. Another finding that is practically pathognomonic of enterocolitis is aeroportia, which is associated with the more severe disease and increased mortality(7). Aeroportia appears as fine ramified lucencies that extend from the hepatic portal region to the liver periphery. One sign of advanced disease is the sign of the persistent loop, which is a dilated bowel loop that remains unchanged in appearance on X-rays for 24 to 36 hours. Another finding is the change of pattern of diffuse loop distension to a pattern of asymmetrical dilation of the intestines. Ascites is a sign of perforation or threat of perforation. No laboratorial test is diagnostic of necrotizing enterocolitis, but severe or persistent thrombocytopenia, neutropenia, coagulopathy, or acidosis may indicate severe disease(8). Some studies evaluated that contrast tests of the gastrointestinal tract, computed tomography, and magnetic resonance are not useful in the clinical investigation of these patients(1-2). The advantages of the abdominal ultrasonography in the study of necrotizing enterocolitis include the non use of ionizing radiation, the possibility of evaluating, in real time, the abdominal structure, particularly the intestines, observing the thickness of the bowel wall, its echogenicity, peristalsis, and perfusion. Ultrasound is more sensitive than conventional radiography for detecting intramural intestinal gas (intestinal pneumatosis), gas in the portal system (aeroportia), and investigating and assessing free or collected fluid in the abdominal cavity(7,9-10). The worst complication of necrotizing enterocolitis is intestinal perforation. A small quantity of gas in the peritoneal cavity or even in the retroperitoneal space, as in the case reported, may not be detected by radiographs, but ultrasonography can demonstrate the presence of free fluid in the abdominal cavity, containing fine debris in suspension, suggesting intestinal perforation. Therefore, ultrasonography may be very useful in the diagnosis of cases in which radiographic

Ultrasonography in diagnosis of necrotizing enterocolitis

improvement is not compatible with the patient’s clinical condition or when there is clinical deterioration with no evidence of pneumoperitoneum on plain film of the abdomen.

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REFERENCES 1. Epelman M, Daneman A, Navarro OM, Morag I, Moore AM, Kim JH, et al. Necrotizing enterocolitis: review of state-of-the-art imaging findings with pathologic correlation. Radiographics. 2007;27(2):285-305. 2. Buonomo C. The radiology of necrotizing enterocolitis. Radiol Clin North Am. 1999;37(6):1187-98.

CONCLUSIONS Necrotizing enterocolitis in neonates is generally detected clinically and radiographically, but at the onset of the disease, classical findings, such as abdominal distention and intestinal pneumatosis may not be detectable by conventional radiography. Therefore, ultrasonography should be a part of the diagnostic investigation armamentarium in cases with suspected necrotizing enterocolitis, due to its low invasiveness, its portability, the fact of not involving ionizing radiation, and especially due to its high sensitivity for detecting changes resulting from intestinal distress, characterizing aeroportia and free fluid in the abdominal cavity. It is believed that ultrasonography is an important diagnostic modality in the evaluation of children with suspected necrotizing enterocolitis.

3. Kim WY, Kim WS, Kim IO, Kwon TH, Chang W, Lee EK. Sonographic evaluation of neonates with early-stage necrotizing enterocolitis. Pediatr Radiol. 2005;35(11):1056- 61. 4. Faingold R, Daneman A, Tomlinson G, Babyn PS, Manson DE, Mohanta A, et al. Necrotizing enterocolitis: assessment of bowel viability with color doppler US. Radiology. 2005;235(2):587-94. 5. Pickworth FE, Franklin K. Case report: ultrasound diagnosis of unsuspected necrotizing enterocolitis. Clin Radiol. 1994;49(9):649-51. 6. Pear BL. Pneumatosis intestinalis: a review. Radiology. 1998;207(1):13-9. 7. Silva CT, Daneman A, Navarro OM, Moore AM, Moineddin R, Gerstle JT, et al.  Correlation of sonographic findings and outcome in necrotizing enterocolitis. Pediatr Radiol. 2007;37(3):274-82. 8. Lin PW, Stoll BJ. Necrotising enterocolitis. Lancet. 2006;368(9543):1271-83. 9. Merritt CR, Goldsmith JP, Sharp MJ. Sonographic detection of portal venous gas in infants with necrotizing enterocolitis. AJR Am J Roentgenol. 1984;143(5):1059-62. 10. Vernacchia FS, Jeffrey RB, Laing FC, Wing VW. Sonographic recognition of pneumatosis intestinalis. AJR Am J Roentgenol. 1985;145(1):51-2.

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