18. Abdominal Mass / S. Grégoire 

When an abdominal mass is discovered on physical examination, one must define its nature. Using a systematic approach often permits the identification of the mass before the use of sophisticated tests.   

Important clues in the history and general physical examination may help to identify the enlarged viscus. For example, in a young patient presenting with diarrhea, weight loss and abdominal pain, finding a right lower quadrant mass would suggest inflammatory bowel disease. However, an abdominal mass may be discovered during physical examination of an asymptomatic individual. Certain observations made during the abdominal examination may be helpful. (See also Section 20.) 

Where is the mass located? A practical approach is to divide the abdomen into four quadrants (see Section 20.1). Starting from the principle that an abdominal mass originates from an organ, surface anatomy may suggest which one is enlarged. A mass seen in the left lower quadrant, for example, could be of colonic or ovarian origin but, unless there is situs inversus, one would not consider an appendiceal abscess! 

Does the mass move with respiration? In the upper abdomen a mobile intra-abdominal mass will move downward with inspiration, while a more fixed organ (e.g., aorta, pancreas) or an abdominal wall mass (e.g., hematoma of rectus muscle) will not.

Is there visible peristalsis?   

Careful auscultation for bowel sounds, bruit or rub over an abdominal mass is part of the systematic approach.     

This is achieved by inspection, percussion and palpation. Is the organ air-filled (e.g., stomach) or fluid-filled? Is it a well-defined mass (e.g., liver, spleen) or are its borders difficult to define (matted loops of small bowel)? Is the surface regular? An enlarged liver due to fatty infiltration may have a smooth surface, while a cirrhotic organ is usually irregular and nodular. What is the consistency of the mass? Firm? Hard or soft? Is it pulsatile? In the absence of ascites, ballottement of an organ situated in either upper quadrant more likely identifies an enlarged kidney (more posterior structure) than hepatomegaly or splenomegaly. 

The following suggests an approach to the differential diagnosis of an abdominal mass located in each quadrant: 

This location suggests liver, right kidney, gallbladder and, less commonly, a colon or gastroduodenal mass. A pancreatic mass is rarely palpable.  

As a subdiaphragmatic organ, the liver moves downward with inspiration. This anterior organ has an easily palpable lower border, which permits assessment of its consistency. A bruit or venous hum can be heard in certain conditions. An enlarged left lobe can usually be felt in the epigastric area 

The kidney may protrude anteriorly when enlarged and be difficult to differentiate from a Riedel’s lobe of the liver. It may be balloted. 

This oval-shaped organ moves downward with inspiration and is usually smooth and regular. 

Colon masses are deep and ill-defined, and do not move with respiration. High-pitched bowel sounds suggest obstruction. 

Location in the left upper quadrant suggests spleen or left kidney. Less commonly, a colonic (splenic flexure) or gastric mass can be felt. A pancreatic mass is rarely palpable. 

This anterior organ moves downward with inspiration. Since it has an oblique longitudinal axis, it extends toward the right lower quadrant when enlarged. It has a medial notch and the edge is sharp. 

Its more posterior position and the presence of ballottement helps distinguish the left kidney from the spleen. 

It is practically impossible to differentiate masses in these by physical examination. The history helps but often one must resort to radiology or endoscopy. 

A mass in this area has its origin either in the lower GI tract (colon, distal small bowel, appendix) or in a pelvic structure (ovary, uterus, fallopian tube). 

These deeper organs are usually ill-defined. Clinical context is important. Inflammatory bowel disease usually would be associated with pain on palpation but carcinoma of the cecum would be painless. 

Bimanual palpation is the preferred method. 

As with a right lower quadrant mass, the differential diagnosis here is between lower GI (in this quadrant the sigmoid colon) and pelvic origin. The shape of the organ and pelvic examination should help differentiate the two. 

To complete the assessment of an abdominal mass, one may choose among several different investigational tools. The use of specific tests depends on availability and on the organ studied. 

Generally, ultrasound is useful. This noninvasive, safe, cheap and widely available method identifies the mass and provides information on its origin and nature. Ultrasound may also be used to direct a biopsy. Other noninvasive modalities are nuclear imaging and CT scan. Hollow organs may be demonstrated radiographically through the use of contrast media (e.g., barium enema, GI series, ultrasound, intravenous pyelogram, endoscopic retrograde cholangiopancreatography, etc.). Sometimes, laparotomy or laparoscopy will be necessary to make the diagnosis.