Tumors and Beyond : an Array of Abdominal Masses in Children

Aims and Objectives: 1. To provide insight into the different pediatric abdominal masses by Computed Tomography. 2. To characterize the various pediatric abdominal masses based on their imaging features. Materials & Methods: This observational study was conducted in Department of Radio-diagnosis at S.P. Medical College & A.G. of Hospitals, Bikaner, Rajasthan. Data for the study was collected from patients of pediatric age group attending/ referred to the department of Radio-Diagnosis. An ultrasonographic examination was done in all cases using GE LOGIQ P5 USG machine. Doppler imaging was done in required cases. Non-contrast and contrast enhanced CT scan of the patients was carried out, using PHILIPS BRILLIANCE MDCT 64 SLICE CT SCAN. Scanning protocol was modified according to the age, weight of the child and the clinical situation. Imaging findings were correlated with the clinical course of disease and/or surgical/ cytological findings. The results were subjected to statistical analysis and expressed as percentages. Conclusion: The recent developments have broadened the usefulness of Computed tomography in the evaluation of pediatric abdominal masses. The advantages of single breath hold acquisition in uncooperative children, improved vessel contrast enhancement, increased detection of lesions, and multiplanar and three dimensional reconstruction may make it one of the modalities of choice in diagnosis of abdominal masses in children.


Introduction
Abdominal lumps in children include a variety of lesions of diverse origin.They may occur from the new born period through adolescence [1].In most cases, there is absence of peculiar signs and symptoms that may aid in timely diagnosis.In many cases, the lesion is detected late after a long period of vague, nonspecific symptoms.The role of radiological imaging is to identify the precise location and extension of the pathologic process using the few essential imaging techniques.
Most abdominal masses in children are initially imaged by Plain X-ray.They provide information about the location of the mass and presence or absence of calcific component [1].Their role ranges from a screening process, providing non-specific information in some cases, to providing specific information in some cases, to providing a specific diagnosis in others [2].However, children are exposed to radiations and have limited role as only four basic densities (bone or mineral, soft tissue, fat, or air) are visualized [3].
Ultrasound is a powerful imaging modality for the pediatric patients since it does not have radiation hazard.It allows imaging in multiple planes, permits repetitive examinations and requires no physiologic function for anatomic visualization [2].It can be used in directing a location for biopsies and drainage of fluid collections [4].It aids in localizing the tumor, looking for associated lymphadenopathy and assessment of vascularity by Colour and Duplex Doppler.Thus, USG is diagnostic in some cases while limits the differential diagnoses in others and hence, is useful as a general screening procedure.However, USG is highly operator dependent and is adversely affected by bone or gas artefacts.In addition, ultrasonography provides less precise anatomic details [4,5,6].
In recent times, computed tomography has found increasing application in the evaluation of pediatric abdominal masses [2].The anatomic detail provided by CT is superior to any other imaging modality currently available.It obtains an entire anatomic section of tissue, which aids in determining the precise extent of disease.It is not operator dependent and permits the accurate measurement of tissue attenuation coefficient.Enhancement with contrast medium facilitates measurement of blood flow to an organ or pathologic abnormality [7,8].However, the paucity of tilt in children makes delineation of anatomic margins in the retroperitoneum difficult [9].In addition, conventional CT requires sedation in infants and small children, intravenous and enteric contrast medium, immobilization and alteration of environment, and is time consuming [10,11].Thus, Multislice helical technology has expanded the usefulness of CT in evaluation of pediatric abdominal masses [12].The advantages of single breath-hold acquisition in cooperative children, improved vascular contrast enhancement, increased detection of parenchymal lesions and multiplaner and three-

Exclusion Criteria
• Patients above the age of 14 yrs.
• Patients with previous history of contrast sensitivity.

Methods
A detailed clinical history was recorded followed by relevant clinical examination.An ultrasonographic examination was done in all cases using GE LOGIQ P5 USG machine.Doppler imaging was done in required cases.Non-contrast and contrast enhanced CT scan of the patients was carried out, using PHILIPS BRILLIANCE MDCT 64 SLICE CT SCAN.Scanning protocol was modified according to the age, weight of the child and the clinical situation.Imaging findings were correlated with the clinical course of disease and/or surgical/cytological findings.The results were subjected to statistical analysis and expressed as percentages.
Next category of masses included those of gastro intestinal /mesenteric origin (Table 7).These constituted 12% (6/50) of total cases as compared to 32% in Rastogi series.However, in cases illustrated by Griscom, 16% cases were of gastrointestinal/ mesenteric origin while Biona series had only 2 such cases [6,16,17].Out of the cases in our study, all 6 children were >5years of age.The diagnosis included mesenteric lymphangioma, chronic midgut volvulus, omphalomeseneric cyst (Figure 4).Hepatobiliary masses contributed 8(16%) cases.Out of these, 2 cases were of hepatoblastoma (Figure 5), one of Hepatocellular carcinoma, and one of choledochal cyst (Figure 6).Cases of liver abscess and hydatid cyst were also observed (Figure 7).Cases involving genital system were also found 6/50 (12%).Of these 1 was malignant (dysgerminoma) while others were benign and included teratoma, ovarian cysts and ovarian tortion (Figure 8).USG and CT were done in every patient.While USG was found quite useful in majority of the cases, its accuracy was found to be consistently less as compared to CT in all aspects.While the accuracy of USG in predicting nature of the mass, its localisation, extent and exact diagnosis was 81%, 64.5%, 59% and 54.5% respectively, the accuracy of CT for same was found to be 100%, 97%, 100% and 81% respectively (Table8, Chart 7).

Conclusion
An abdominal mass in an infant presents a challenging diagnostic problem.Preoperative study of abdominal masses is a problem of primary importance in paediatric age group [20].
In last many years, Computed Tomography has been established as the imaging modality of choice for evaluation of paediatric abdominal masses [21].Recently the introduction of multisclice multidetector helical CT has resulted in improved spacial and temporal resolution with reduction in scan acquisition and display time from minutes to seconds, while at the same time allowing acquisition of volume data [22,23].
While CT was found to be 100% accurate in determining the exact location as well as extent of the mass lesions, the accuracy for diagnosis was found to be 81% reflecting the inherent limitation of the imaging modality in terms of non specific findings in certain lesions.An important aspect was optimal vascular enhancement and excellent multiplanar reconstructions with CT that enabled an appropriate evaluation of the extent of the lesion as well as relation of the mass to various vessels at the same time also conclusively telling about vascular invasion, an important finding in context of various malignancies and their staging [24,25].In context of children, the motion artifacts encountered in our study were very infrequent and in no case were they of such significance as to impede the diagnostic value of the examination.
Thus we would conclude that the recent advances have expanded the usefulness of CT in the evaluation of paediatric abdominal masses [26,27].The advantage of single breath hold acquisition in cooperative children, improved vascular contrast enhancement, increased detection of parenchymal lesions, and multiplanar and three dimensional reconstruction may make it one of the modalities of choice in evaluation of paediatric abdominal masses.

Chart 1 :
Age Distribution

Chart 2 :
Sex distribution among the casesMajority of the patient presented with progressively increasing abdominal lump (Table

Figure 1 (
Figure 1 (Wilm's Tumor): Clockwise: On sagittal US image of the left kidney, a large mass can be demonstrated as a hypoechoic mass in the upper pole of the kidney.Reformatted coronal and axial contrast-enhanced CT images demonstrate a larger mass with well-defined contours in the upper pole of the left kidney.There is a nodular heterogeneous lymph node in para-aortic region.

Figure 2 (
Figure 2 (Renal abscess): Right: Transverse ultrasound image of right kidney shows avascular heterogeneous area in upper and mid zones.Left: Contrast-enhanced axial CT image shows heterogeneous lesion with multiple internal septations of varying thickness in right kidney.

Figure 3 (
Figure 3 (Neuroblastoma): Neuroblastoma; Axial CT scans shows a large soft tissue mass, with areas of necrosis, crossing the midline and encasing and anteriorly displacing the aorta and inferior vena cava Figure 5 (Hepatoblastoma): Axial Contrast enhanced CT shows heterogeneously enhancing mass lesion in the left lobe of liver.

Figure 4 (
Figure 4 (Mesenteric cyst): Transverse ultrasound image of mid abdomen shows large anechoic cystic mass with imperceptible wall.Contrast-enhanced axial CT image shows well-circumscribed cystic mass without enhancement inmidabdomen.

Figure 6 (
Figure 6 (Choledochal cyst): CT scan of a child shows a well-defined cyst in the porta hepatis associated with dilated central hepatic ducts.

Figure 7 (
Figure 7 (Hydatid cyst of liver): Contrast-enhanced axial CT image shows well-defined cystic mass with several internalendocyst membranes.

Figure 8 (
Figure 8 (Ovarian Cyst): Axial CT shows a large ovarian cyst displacing and compressing the urinary bladder is typically hypodense, sharply demarcated with a smooth thin wall.

Table 2 :
Sex distribution

Table 1 :
Age Distribution Maximum: More than 1yr Biona et.al, in 1983 and Rastogi et.al in 1988 reviewed the pattern of paediatric abdominal masses

Table 3 :
Various clinical signs/symptoms of presentation

Table 5 :
Distribution of masses according to nature

Table 4 :
Initial investigation for which patient was referred Maximum: USG-88%Chart 4: Initial investigation requested Chart 5: Distribution of masses according to nature

Table 6 :
Location of masses Chart 6: Showing location of masses in various age groups

Table 7 :
Percentage of masses according to diagnosis

Table 8 :
Accuracy of CT and USG vis-à-vis surgical/cytological findings