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Pediatrics - Abdominal Mass
Basics
Description
An abdominal mass is an abnormal lump, swelling, or area of fullness within the abdominal cavity that may be identified through physical examination or diagnostic imaging.
The mass may arise from an abdominal organ or develop independently of the abdominal viscera. Its origin may be within the peritoneal cavity or the retroperitoneal space.
Epidemiology
The causes of abdominal masses in children are diverse and vary according to the patient’s age and the anatomical location of the lesion.
Most pediatric abdominal masses are caused by conditions that do not require surgical intervention. Constipation is one of the common benign causes.
Approximately 57% of abdominal masses in children are associated with organ enlargement, particularly hepatomegaly or splenomegaly.
In infants, abdominal masses frequently originate from the kidneys and are usually benign. Hydronephrosis is a common example. However, Wilms tumor remains the most common malignant renal tumor in childhood.
Hepatic masses account for approximately 5–6% of pediatric intra-abdominal masses. Hepatoblastoma is the most common primary malignant liver tumor in children and typically presents between 1 and 3 years of age.
Risk Factors
Certain hereditary disorders and genetic syndromes increase the risk of developing abdominal tumors.
Children with Beckwith-Wiedemann syndrome, WAGR syndrome (Wilms tumor, aniridia, genitourinary abnormalities, and intellectual disability), and Denys-Drash syndrome have an increased risk of developing Wilms tumor.
Patients with these conditions require regular tumor surveillance according to established screening protocols to facilitate early detection and management.
General Prevention
Preventive measures depend on the underlying cause of the abdominal mass and whether the contributing factors can be modified.
For example, when a mass develops as a result of a retained foreign body, educating parents and children about preventing accidental ingestion may help reduce recurrence.
For congenital abnormalities, hereditary disorders, or neoplastic conditions, primary prevention may not be possible. Early recognition and appropriate surveillance are therefore important.
Pathophysiology
The pathophysiological mechanisms responsible for abdominal masses vary according to the underlying disease and the anatomical structures involved.
An abdominal mass may result from organ enlargement, congenital malformations, abnormal tissue proliferation, cyst formation, fluid accumulation, inflammation, vascular disturbances, or obstruction of hollow organs.
Etiology
The differential diagnosis of an abdominal mass in children can be classified according to the organ or anatomical region involved.
Stomach
Gastric distension or delayed gastric emptying, also known as gastroparesis, may cause enlargement of the stomach and present as an abdominal mass.
Other gastric causes include gastrointestinal duplication cysts, retained foreign bodies, bezoars, and gastric torsion.
Although uncommon, gastric neoplasms such as lymphoma and sarcoma may also produce palpable abdominal masses.
Intestine
Intestinal causes include fecal accumulation resulting from constipation or fecal impaction.
Abnormal intestinal dilatation, including toxic megacolon, may produce considerable abdominal enlargement.
Other obstructive or congenital conditions include foreign bodies, meconium ileus, intestinal duplication cysts, volvulus, intussusception, intestinal atresia, intestinal stenosis, and intestinal malrotation.
Inflammatory conditions may also cause abdominal masses, particularly complications of inflammatory bowel disease such as intra-abdominal abscesses and inflammatory phlegmon.
Additional causes include appendicitis, Meckel diverticulum, abscesses associated with Meckel diverticulum, and duodenal hematoma following abdominal trauma.
Intestinal tumors that may present as abdominal masses include lymphoma, adenocarcinoma, gastrointestinal stromal tumors, and neuroendocrine tumors such as appendiceal carcinoid tumors.
Liver
Hepatic masses may result from hepatomegaly, cystic abnormalities, vascular lesions, infiltrative disorders, or neoplastic disease.
Intrinsic Liver Disease: Hepatomegaly may occur with infectious or autoimmune hepatitis and metabolic disorders such as Wilson disease and glycogen storage disease.
Infiltrative Disorders: Cystic lesions, tumors, and other infiltrative processes may increase the size of the liver.
Biliary Obstruction: Impaired bile drainage may produce hepatomegaly and associated hepatobiliary abnormalities.
Vascular Disorders: Hepatic venous obstruction or congestion may occur in Budd-Chiari syndrome and congestive heart failure.
Cystic Liver Disease: Congenital or acquired cystic abnormalities, including Caroli disease, may present as hepatic masses.
Solid Hepatic Tumors: Important examples include hepatoblastoma, hepatocellular carcinoma, hepatic adenoma, and other systemic or diffuse neoplastic processes involving the liver.
Vascular Tumors: Hepatic hemangiomas and hemangioendotheliomas may cause focal or diffuse hepatic enlargement.
Other Benign Lesions: Hepatic hamartomas and focal nodular hyperplasia are additional causes of localized liver masses.
Gallbladder And Biliary Tract
Abnormalities involving the gallbladder and biliary system may present as right upper abdominal masses.
Possible causes include choledochal cysts and gallbladder hydrops.
Biliary obstruction resulting from gallstones, strictures, or traumatic injury may also cause gallbladder enlargement or other palpable abnormalities.
Spleen
Splenic masses may arise from congenital cysts or generalized enlargement of the spleen.
Storage disorders such as Gaucher disease and Niemann-Pick disease may lead to significant splenomegaly.
Other causes include Langerhans cell histiocytosis and hematologic malignancies such as leukemia.
Hemolytic disorders, including sickle cell disease, hereditary spherocytosis, and other red blood cell abnormalities, may also produce splenic enlargement.
Portal hypertension and wandering spleen are additional conditions that may present as abdominal masses.
Pancreas
Pancreatic masses may arise from congenital pancreatic cysts or pseudocysts associated with pancreatitis or abdominal trauma.
Neoplastic causes include pancreatoblastoma and pancreatic neuroendocrine tumors, such as insulinomas and gastrinomas.
Solid pseudopapillary neoplasms are another potential cause of pancreatic masses in children.
Kidney
Renal abnormalities are particularly important causes of abdominal masses in neonates and infants.
Hydronephrosis and ureteropelvic junction obstruction may result in significant renal enlargement.
Congenital renal disorders include multicystic dysplastic kidney and polycystic kidney disease.
Renal neoplasms include congenital mesoblastic nephroma, Wilms tumor, and renal cell carcinoma.
Other potential causes include renal vein thrombosis and cystic nephroma.
Bladder
Significant bladder distension or urinary retention may present as a palpable suprapubic mass.
Neurogenic bladder dysfunction is another possible cause of abnormal bladder enlargement.
Adrenal Glands
Adrenal masses may arise from adrenal hemorrhage, adrenal abscesses, or neoplastic conditions.
Important adrenal tumors include neuroblastoma and pheochromocytoma.
Uterus
Pregnancy should be considered as a possible cause of lower abdominal enlargement in adolescent girls.
Other uterine or genital tract abnormalities include hematocolpos, hydrocolpos, and hydrometrocolpos, which involve the accumulation of blood or fluid within the reproductive tract.
Ovaries
Ovarian abnormalities may present as pelvic or lower abdominal masses.
Possible causes include follicular cysts, dermoid cysts, ovarian torsion, and ovarian germ cell tumors.
Peritoneal Cavity
Ascites, which represents abnormal fluid accumulation within the peritoneal cavity, may cause generalized abdominal enlargement.
Intra-abdominal teratomas may also present as palpable abdominal masses.
Abdominal Wall
Abdominal wall masses may be associated with congenital defects, hernias, traumatic injuries, or tumors.
Potential causes include umbilical hernias, inguinal hernias, ventral hernias, omphalocele, and gastroschisis.
Other abnormalities include urachal cysts and rectus sheath hematomas resulting from trauma.
Abdominal wall tumors include fibromas, lipomas, and rhabdomyosarcomas.
Omentum And Mesentery
Masses arising from the omentum or mesentery may include omental cysts, mesenteric cysts, mesenteric fibromatosis, and mesenteric adenitis.
These conditions may produce localized abdominal fullness or a palpable mass.
Other Causes
Additional neoplastic conditions include liposarcoma, leiomyosarcoma, fibrosarcoma, and mesothelioma.
Other uncommon causes include torsion of an intra-abdominal undescended testicle, lymphangioma, fetus in fetu, and sacrococcygeal teratoma.
Diagnosis
Diagnostic Approach
The evaluation of a child with an abdominal mass requires a systematic approach to identify the underlying cause, determine the anatomical origin, and recognize conditions requiring urgent intervention.
Phase 1: Clinical Assessment
The initial evaluation involves obtaining a comprehensive medical history and performing a detailed physical examination.
The history should establish the onset, duration, progression, and associated symptoms of the abdominal mass.
A thorough abdominal examination should be performed to determine the approximate location, size, consistency, mobility, and tenderness of the lesion.
These clinical findings help narrow the differential diagnosis and guide subsequent investigations.
Phase 2: Diagnostic Investigations
Abdominal radiography may be performed to assess suspected intestinal obstruction, fecal accumulation, abnormal bowel gas patterns, or displacement of surrounding structures.
Abdominal ultrasonography is particularly useful for identifying the organ of origin and determining whether the mass contains solid, cystic, or hemorrhagic components.
Laboratory investigations should be selected according to the child’s clinical presentation and the suspected underlying disorder.
Important Diagnostic Considerations
Constipation: Severe constipation or fecal impaction may produce a large, firm abdominal mass extending upward from the pubic region.
Normal Liver Palpation In Neonates: A palpable liver edge may be a normal finding in newborns. The total liver span should be assessed before diagnosing hepatomegaly.
Bladder Distension In Infants: A distended urinary bladder may be mistaken for an abdominal tumor or another intra-abdominal mass.
Gastric Distension: Gastric enlargement should be considered in children presenting with a tympanitic epigastric mass.
Splenomegaly: An enlarged spleen may indicate an underlying systemic infection or malignancy, including Epstein-Barr virus infection or lymphoma.
History
Children with abdominal masses may be asymptomatic or may present with symptoms related to the affected organ or underlying disease.
A focused history can help distinguish benign conditions from inflammatory, obstructive, traumatic, and malignant causes.
Weight Loss
Unexplained weight loss may suggest malignancy or a chronic inflammatory disorder, particularly inflammatory bowel disease.
Fever
Fever may indicate an infectious process, inflammatory disease, or underlying malignancy.
Jaundice
Jaundice may suggest hepatobiliary disease, biliary obstruction, or a hematologic disorder associated with increased red blood cell destruction.
Hematuria Or Dysuria
Blood in the urine or painful urination may indicate renal or urinary tract disease.
Vomiting, Bilious Vomiting, Or Early Satiety
Vomiting, particularly bilious vomiting, may indicate intestinal obstruction.
Early satiety may occur when an abdominal mass compresses the stomach or surrounding gastrointestinal structures.
Bilious vomiting in a child requires urgent assessment because it may indicate a potentially serious intestinal obstruction.
Abdominal Pain
Abdominal pain may be associated with constipation, appendicitis, intussusception, or intestinal obstruction.
The location, severity, duration, and pattern of pain may help narrow the differential diagnosis.
Frequency And Characteristics Of Bowel Movements
Changes in bowel movement frequency, stool consistency, or defecation patterns may indicate constipation, intussusception, or intestinal compression caused by an abdominal mass.
Bleeding Or Easy Bruising
Abnormal bleeding or bruising may suggest liver disease, coagulation abnormalities, or hematologic disorders.
Pallor Or Weakness
Pallor, weakness, or fatigue may indicate anemia or ongoing blood loss.
History Of Abdominal Trauma
Previous abdominal trauma may lead to pancreatic pseudocyst formation or duodenal hematoma.
Sexual Activity
A confidential and developmentally appropriate sexual history is important in adolescents when pregnancy is possible.
Pregnancy and pregnancy-related complications should be considered during the evaluation of lower abdominal or pelvic masses.
Age Of The Patient
The patient’s age is an important factor in determining the most likely causes of an abdominal mass.
Neonates: Most abdominal masses originate from the genitourinary system. Common examples include hydronephrosis and congenital cystic renal abnormalities.
Adolescent Girls: Ovarian disorders, hematocolpos, and pregnancy become important diagnostic considerations.
Malignant Abdominal Tumors According To Age
Infants: Neuroblastoma and Wilms tumor are important malignant causes of abdominal masses.
Children: Wilms tumor, sarcomas, and germ cell tumors should be considered.
Children Older Than 10 Years: Sarcomas, germ cell tumors, and abdominal lymphomas are important malignant diagnoses.
Physical Examination
A comprehensive examination is essential for evaluating the characteristics of the abdominal mass and identifying evidence of systemic disease.
General Appearance
A child who appears acutely unwell or demonstrates significant weight loss or cachexia may have an underlying infectious or malignant condition.
The child’s hydration status, nutritional condition, and overall clinical stability should also be assessed.
Location Of The Abdominal Mass
The anatomical position of the mass provides important clues regarding the likely organ or structure involved.
Left Lower Quadrant: Possible causes include fecal impaction, ovarian abnormalities, and ectopic pregnancy.
Left Upper Quadrant: Splenomegaly and abnormalities involving the left kidney should be considered.
Right Lower Quadrant: Potential causes include appendicitis, inflammatory bowel disease-associated abscesses, intestinal phlegmon, intussusception, ovarian pathology, and ectopic pregnancy.
Right Upper Quadrant: Masses may arise from the liver, gallbladder, biliary tract, or intestine.
Epigastric Region: Possible causes include gastric bezoars, gastric torsion, pancreatic pseudocysts, and hepatomegaly.
Suprapubic Region: Consider pregnancy, hematocolpos, hydrometrocolpos, urinary retention, and posterior urethral valves.
Flank Region: Renal abnormalities such as hydronephrosis, cystic kidney disease, and Wilms tumor are important considerations.
Characteristics Of The Abdominal Mass
The mass should be evaluated for size, shape, consistency, mobility, tenderness, surface texture, and relationship with surrounding structures.
These characteristics may help distinguish inflammatory, cystic, obstructive, and neoplastic conditions.
Hard And Immobile Mass
A firm mass that is fixed to surrounding structures may raise suspicion for a neoplastic process.
Extension Across The Midline Or Into The Pelvis
An abdominal mass extending across the midline or into the pelvis may occur with certain tumors or significant enlargement of the liver or spleen.
Percussion Findings
Percussion may help determine whether the underlying structure contains solid tissue, fluid, or gas.
Dullness generally suggests a solid or fluid-filled structure, whereas tympany indicates the presence of gas within a hollow organ.
Shifting Dullness And Fluid Wave
The presence of shifting dullness or a fluid wave may indicate ascites.
Skin Examination
Bruising and petechiae may occur with coagulation abnormalities related to liver disease or malignant infiltration of the bone marrow.
Café-au-lait macules may be associated with neurofibromatosis and neurofibromas.
Lymphadenopathy Or Lymphadenitis
Enlarged or inflamed lymph nodes may indicate an underlying systemic infection or malignancy.
Peritoneal Signs
Guarding, rebound tenderness, or other signs of peritoneal irritation may indicate appendicitis, complicated intestinal obstruction, or gastrointestinal perforation.
These findings require urgent surgical evaluation.
Rectal Bleeding
Rectal bleeding may result from intestinal inflammation, polyps, or other lesions involving the gastrointestinal tract.
Diagnostic Tests And Interpretation
Diagnostic investigations should be individualized according to the child’s clinical presentation, suspected organ of origin, and possible underlying disease.
Initial Laboratory Investigations
Complete Blood Count With Differential
A complete blood count may reveal anemia, evidence of hemolysis, or abnormalities suggestive of infectious or hematologic disease.
Blood Chemistry And Organ Function Tests
Renal Function: Blood urea nitrogen and serum creatinine measurements are useful for evaluating suspected renal abnormalities.
Liver Function: Investigations may include bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, gamma-glutamyl transferase (GGT), albumin, prothrombin time (PT), and partial thromboplastin time (PTT).
Gallbladder And Biliary Disease: Serum bilirubin and GGT measurements may help evaluate suspected biliary abnormalities.
Pancreatic Disease: Serum amylase and lipase may be elevated in pancreatitis or other pancreatic disorders.
Intestinal Disease: Hypoalbuminemia may occur in certain gastrointestinal conditions.
Uric Acid And Lactate Dehydrogenase
Elevated serum uric acid and lactate dehydrogenase (LDH) levels may reflect rapid cellular turnover, including that associated with certain malignant tumors.
Quantitative Serum Beta-Human Chorionic Gonadotropin
Serum β-hCG testing can identify pregnancy and may also be elevated in selected germ cell tumors.
Alpha-Fetoprotein
Elevated serum alpha-fetoprotein (AFP) may support the diagnosis of hepatoblastoma in the appropriate clinical setting.
AFP values must be interpreted according to the child’s age because physiologically elevated concentrations occur during infancy.
Urinalysis
Hematuria or proteinuria may suggest a renal or urinary tract origin for the abdominal mass.
Diagnostic Imaging
Plain Abdominal Radiography
Abdominal radiographs may demonstrate features of intestinal obstruction, including dilated bowel loops and air-fluid levels.
They may also help identify abnormal bowel gas patterns, calcifications, fecal impaction, and displacement of intestinal structures by an abdominal mass.
Significant urinary retention may occasionally produce associated radiographic findings.
Ultrasonography
Ultrasonography is commonly the preferred initial imaging investigation for a pediatric abdominal mass.
It helps identify the organ of origin and differentiate solid lesions from cystic or fluid-filled structures.
Doppler ultrasonography can assess the vascularity of the lesion and identify associated blood flow abnormalities.
Ultrasonography may also be used to guide biopsy procedures when tissue sampling is required.
Limitations include dependence on operator expertise and reduced visualization when overlying bowel gas obscures deeper structures.
Computed Tomography
Computed tomography (CT) provides detailed cross-sectional images and may be particularly useful when bowel gas or adjacent bone limits other imaging techniques.
It helps determine the anatomical extent of a mass and its relationship with neighboring organs and structures.
When malignancy is suspected, imaging of the chest, abdomen, and pelvis may be required according to tumor-specific staging protocols.
The potential risks associated with ionizing radiation should be considered when selecting CT imaging in children.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is especially useful for characterizing complex soft tissue masses, vascular lesions, and tumors involving the liver or major abdominal blood vessels.
It provides detailed anatomical information without exposure to ionizing radiation.
Nuclear Medicine Investigations
Hepatobiliary Scintigraphy: A hepatobiliary iminodiacetic acid (HIDA) scan may be used to assess selected disorders involving the liver, gallbladder, and biliary tract.
Meckel Scan: A radionuclide study may identify ectopic gastric mucosa within a Meckel diverticulum or certain intestinal duplication cysts.
Renal Nuclear Imaging: Selected radionuclide investigations may help assess renal function, drainage, and anatomical abnormalities.
Fluoroscopic Studies
Upper Gastrointestinal Contrast Studies: These investigations may assist in identifying intestinal malrotation or selected causes of gastrointestinal obstruction.
Contrast Enema: This examination may provide useful information in selected conditions involving the colon or intestinal obstruction.
Voiding Cystourethrogram: A VCUG may be performed to assess urinary tract abnormalities, including posterior urethral valves and vesicoureteral reflux.
Treatment
General Measures
Management of pediatric abdominal masses depends on the underlying cause, anatomical location, and severity of the child’s clinical condition.
Immediate hospital evaluation is necessary when an abdominal mass is accompanied by significant dehydration, intestinal obstruction, active bleeding, feeding intolerance, or clinical deterioration.
Initial management includes stabilization of the patient, appropriate laboratory investigations, and diagnostic imaging.
Consultation with pediatric surgery is indicated when a surgical condition is suspected.
Pediatric oncology consultation should be obtained when clinical findings or investigation results raise concern for malignancy.
Other abdominal masses require prompt evaluation and referral to appropriate pediatric subspecialists according to the suspected anatomical origin and underlying diagnosis.
Issues For Referral
With the exception of clearly established uncomplicated constipation, a newly detected abdominal mass in a child generally requires prompt medical assessment.
Diagnostic investigations should be arranged without unnecessary delay, preferably at a pediatric healthcare facility or through clinicians experienced in evaluating childhood abdominal disorders.
Children with suspected malignant disease should be referred to pediatric oncology services.
Those with possible surgical emergencies require urgent pediatric surgical consultation.
The urgency of referral should be determined by the child’s clinical stability, associated symptoms, and likelihood of an underlying serious condition.
Admission, Inpatient, And Nursing Considerations
Hospital admission is indicated for children with abdominal masses associated with acute abdominal symptoms, systemic illness, or significant physiological compromise.
Intestinal Obstruction And Acute Abdominal Conditions
Children presenting with abdominal distension, persistent vomiting, severe pain, or signs of peritoneal irritation may require immediate hospitalization.
Conditions requiring urgent evaluation include intussusception, volvulus, gastric torsion, obstructing bezoars, retained gastrointestinal foreign bodies, and appendicitis.
Toxic Megacolon
Toxic megacolon is a severe and potentially life-threatening complication of intestinal inflammation that requires emergency inpatient management.
Ovarian Torsion
Suspected ovarian torsion requires urgent surgical or gynecologic assessment because delayed treatment may compromise ovarian viability.
Ectopic Pregnancy
Ectopic pregnancy should be considered in adolescents who may be pregnant and present with abdominal pain, pelvic masses, or abnormal vaginal bleeding.
Urgent evaluation is essential because rupture may cause life-threatening internal hemorrhage.
Biliary Obstruction
Gallstones, gallbladder hydrops, and other causes of significant biliary obstruction may require hospital-based investigations and treatment.
Fever
Fever accompanying an abdominal mass may indicate an intra-abdominal infection, abscess, or systemic inflammatory condition requiring inpatient care.
Anemia And Coagulopathy
Significant anemia, active bleeding, or coagulation abnormalities may require hospitalization for stabilization, monitoring, and management of the underlying disorder.
Pancreatitis And Pancreatic Pseudocyst
Children with pancreatitis or symptomatic pancreatic pseudocysts may require inpatient monitoring, supportive treatment, and specialist assessment.
Other Abdominal Masses
Other causes of abdominal masses require timely diagnostic evaluation and appropriate specialist referral.
Admission decisions should be based on the suspected underlying diagnosis, symptom severity, and overall clinical stability.
Ongoing Care
Follow-Up Recommendations
Long-term management and follow-up depend on the type, location, and underlying cause of the abdominal mass.
Children with benign, self-limiting conditions may require only short-term clinical follow-up.
Those with congenital abnormalities, persistent masses, or neoplastic conditions may require repeated imaging, laboratory investigations, specialist surveillance, or ongoing treatment.
The frequency and duration of follow-up should be individualized according to the diagnosis, response to treatment, and risk of recurrence.
