Acute abdominal pain is defined as pain in or over the abdominal cavity experienced for anything between few hours and a few weeks [4]. The time interval is necessarily blurred but majority of patients present between six and eight hours after developing pain. Although ultrasound remains the primary modality for the diagnosis of causes of acute abdominal pain in paediatric patients, it has potential drawbacks including operator dependence, poor image quality in obese children, which is becoming a significant problem [11, 12]. Given that there may be cases in which ultrasound is nondiagnostic or difficult to perform, the development of an alternative approach to CT, the usual next imaging choice, is warranted because of the growing awareness of the negative effects of radiation exposure associated with medical imaging in paediatric patients. The IR(MER) regulations of 2000 declare that the justifying practitioner must assess the risks and benefits of other techniques involving less exposure [13]. It is therefore the obligation for radiologists to consider MR as an alternative to CT in cases of acute abdominal pain, particularly in paediatric patients. Our study investigated the feasibility of rapid unenhanced abdominal and pelvic MRI in the evaluation of children with acute abdominal pain and compared these findings with surgical/lab findings and evaluated sensitivity and specificity of MRI in acute abdominal pain in paediatric age group.
Acute appendicitis is the most common cause of acute abdominal pain and the most common surgical condition encountered in paediatric age group. In our study, appendicitis was identified in all the 3 children who presented with pain in right iliac fossa and showed rebound tenderness. Appendicitis was seen as an enlarged appendix with appendiceal diameter greater than 7 mm with a thickened and oedematous wall (Fig. 1) with adjacent inflammatory changes which were best seen on T2-weighted images with fat suppression. MRI offers superior contrast resolution relative to any other available diagnostic modality. As a result detection of even small amounts of fluid and mild inflammation is possible even without the use of intravenous contrast material. Periappendiceal inflammation is a hallmark of acute appendicitis and is readily detectable on the T2-weighted fluid sensitive sequences as high signal in the soft tissues adjacent to the appendix. In one of the children who presented with acute pain in right iliac region, there were features suggesting appendicular perforation. Axial SS-TSE image demonstrated a focal walled off fluid collection with adjacent inflammatory changes (Fig. 2). Cross-sectional imaging has the benefit of detecting the appendix in cases when abnormally positioned, such as in the left abdomen in a patient with malrotation or pelvic positioning of appendix. This is in accordance with the results of Johnson et al. [14] who proved that Ultrafast 3-T MRI is a feasible alternative imaging modality for the diagnosis of acute appendicitis in children, in cases where ultrasound is equivocal or nondiagnostic. The normal appendix on MRI is visible as a blind-ending tubular structure arising from the cecum. The normal appendix may be filled with air (low T2 signal in an nondependent position) or fluid. Inherent non-visualization of the appendix due to adjacent bowel or lack of intraperitoneal fat implies that the appendix is not inflamed or enlarged. Essentially, an inflamed appendix will almost certainly be visible on MRI.
6 patients presented with pain in inguinal region which was acute in onset. Ovarian torsion was identified in 3 of them. Ovarian torsion results from twisting of the ovary and its vascular pedicle on its ligamentous support, and it can result in ischemia or infarction with permanent adverse effects on fertility. Early diagnosis and surgical intervention are critical in salvaging ovarian function. However, the clinical findings in children may be nonspecific, mimicking more common intestinal or urologic abnormalities, and CT or MRI is used as the initial imaging study [15, 16]. In addition, MRI may be requested as a next step in cases where there is incomplete characterization of the ovaries on ultrasound, CT, or both. In our study three MRI findings of ovarian torsion included enlarged, edematous ovary, twisted pedicle, and ovarian hemorrhage (Fig. 3). A torsed ovary showed central edema and prominent peripheral cysts, which were best seen on a T2-weighted sequence through the pelvis. Sintim-Damoa et al. [16] conducted study in which it was suggested that ovarian torsion findings are best seen on T2 weighted images with fat suppression. In 2 of these patients MRI findings suggested the features of hemorrhagic cyst which on follow up proved to be the same (Fig. 4).
1 of these patient, who presented with acute inguinal pain which was periodical showed the features of hematometra on MRI (Fig. 5) and 1 patient showed the features of tubo-ovarian abscess (Fig. 6). The axial T2WI(A) in this patient showed encapsulated hyperintense contents, appearing hypointense on T1W images (B) and displaying restricted diffusion on DW images (C) with low ADC values on ADC map(D).
2 boys presented with the acute onset pain in scrotal region and testicular torsion was suspected in those patients. 1 patient had MRI findings of testicular torsion. Testicular torsion requires emergency surgical treatment because any delay in surgical intervention may result in irreversible testicular damage due to impaired testicular blood flow [17]. MRI findings in patient were low signal intensities with spotty or streaky patterns in fat-suppressed T2-weighted (Fig. 7). The testicular torsion was proved after surgery.
1 patient after having acute abdominal pain was diagnosed with meckel’s diverticulum. He underwent MRI. No significant findings were suggested on MRI, but proved to be meckel’s diverticulum after surgery on histopathology.
Although uncommon in young children, acute cholecystitis is another cause of abdominal pain that requires surgical consultation. Acute cholecystitis is often caused by an impacted gallstone at the gallbladder neck or within the cystic duct. The MRI findings of acute cholecystitis in present study included distended fluid-filled gallbladder with gallstones, gallbladder wall thickening, gallbladder wall edema, and pericholecystic fluid. Gallstones and gallbladder wall thickening were best seen on fat sat T2. Pericholecystic fluid and gall-bladder wall edema were best seen on fat-suppressed single-shot T2-weighted sequence. Loud et al. [18] described the similar findings of acute cholecystitis on MRI in pediatric age group.
MRI provides rapid, accurate identification of small-bowel obstruction and assists in the determination of cause without exposing the patient to radiation. MRI also utilizes intraluminal air as a natural contrast agent and is not limited by previous administration of barium. The diagnosis of small-bowel obstruction on MRI is similar to CT and involves identifying dilated loops of bowel proximal to the obstruction, a distinct transition point, and normal caliber or collapsed bowel distally (Fig. 8). Multiplanar capabilities of MRI allow visualization of the cause of small-bowel obstruction. Rapid scanning with MRI using the HASTE sequence can, within seconds, evaluate small-bowel obstruction with a high degree of accuracy [19].
Pancreatitis is a common pediatric presentation and its prevalence is increasing. There is significant morbidity associated with this condition. In adults, CT is considered the most appropriate staging modality for acute pancreatitis with or without necrosis; however, MRI is increasingly preferred for the pediatric population [20]. The imaging findings on MRI in our study were pancreatic enlargement with loss of the usual lobular appearance of the pancreatic margins resulting in a sausage like appearance and subtle parenchymal signal changes of relative T2 hyperintensity and T1 hypointensity with mild diffusion restriction suggesting the diagnosis (Fig. 9). Jae-Yeon Hwang et al. [21] described the imaging features in pediatric patients having pancreatitis. They found that the signal intensity of the inflamed pancreas is high on T2-weighted images, but remains normal or slightly low on T1weighted fat-suppressed images depending on the severity of pancreatic inflammation.
Acute urinary tract obstruction caused by urolithiasis is frequently seen in adults, although recent studies have shown an increased prevalence even in the pediatric age group. Most children present with acute flank pain that may be accompanied by hematuria. Typical locations of obstructive stones in the urinary tract include the ureteropelvic junction, the ureter at the level of the pelvic brim, and the ureterovesical junction. Management of obstructive urolithiasis is based on clinical features, the size and location of the stones, stone composition, and renal function. The obstructive stone itself often is not identified on MRI because most stones are small and have low signal on all sequences [21]. In our study, we were able to visualise the exquisite details of ureteric dilation, periureteric edema, dilated renal pelvis and calyces, renal edema, and presence of perinephric edema due to high contrast resolution with coronal and axial T2-weighted sequences. Chung et al. [22] also described similar findings on MRI in acute urinary tract conditions. Another condition which can cause acute urinary obstruction is pelvi-ureteric junction obstruction (Fig. 10).
