Lower Abdomen: Anatomy and Causes of Pain
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Introduction
There are many different conditions that can cause abdominal pain, which may make it challenging to diagnose the problem.
Certain characteristics can provide clues to the cause of the abdominal pain:
Location of the pain (right sided, left sided, upper, lower, etc)
Type of pain (crampy, sharp, dull, stabbing, burning, etc)
Associated symptoms (diarrhea, bloating, nausea, vomiting, blood in stool, etc)
Associated factors (after eating, exercise induced, during pregnancy, etc)
The abdomen is a large area, so this EZmed post will focus on the lower abdomen including the anatomy and quadrants of the lower stomach.
We will also discuss causes of lower abdominal pain such as appendicitis, ectopic pregnancy, urinary tract infections, sexually transmitted diseases (STDs/STIs), kidney stones, ovarian torsion, diverticulitis, colitis, etc.
If you would like a comprehensive overview of the entire abdomen, including the anatomy and causes of pain to the upper and mid stomach as well, then check out the following EZmed post:
“Abdominal Pain Causes by Location: The Stomach Grid”.
Let’s get started!
Lower Abdominal Quadrants
As mentioned above, there are many different causes of abdominal pain which can make it challenging to determine the underlying process.
The location of the pain is important to consider as this can help distinguish potential causes.
The simplest way to determine the location is to divide the abdomen into 9 different regions using a 3 x 3 grid as demonstrated below.
We will focus on the lower regions in this post.
Inferior Row
The right lower section is the right lower quadrant (RLQ) - also known as the right iliac region.
The central lower section is the suprapubic region - sometimes referred to as the hypogastric region.
Lastly, the left lower section is the left lower quadrant (LLQ) - or left iliac region.
Image: The lower abdomen can be divided into the following regions: The right lower quadrant (RLQ), suprapubic region, and left lower quadrant (LLQ).
Lower Abdominal Anatomy
Now that we have divided the lower abdomen into different regions, let’s discuss the anatomy of each section.
The below image can be used as a reference.
**We will focus on the main organs and not every single micro-structure. Also note that portions of structures can extend into other regions as well.
Right Lower Quadrant
The right lower quadrant contains the appendix and cecum in both males and females.
The cecum is a pouch-like structure considered to be the first region of the large intestine where the small intestine joins.
The right ovary and fallopian tube are also located in the right lower quadrant in females.
Portions of the small intestine, ascending colon, and right ureter may also extend into the RLQ.
Suprapubic
The suprapubic region contains the bladder in both males and females.
The uterus and associated reproductive structures are also located in the suprapubic region in females, while the prostate and associated reproductive structures are located in the suprapubic region in males.
Portions of the small intestine, right and left ureters, and aorta/iliac arteries may also extend into the suprapubic region.
Left Lower Quadrant
The left lower quadrant is similar to the right lower quadrant with several differences.
First, there is no appendix (RLQ structure).
Second, the sigmoid portion of the colon is located in the left lower quadrant rather than the cecum.
Third, the left ovary and fallopian tube are located here in females rather than right.
Portions of the small intestine, descending colon, and left ureter may also extend into the LLQ.
Image: The main structures of the RLQ include the appendix and colon (cecum/ascending) in males and females, and the right ovary/fallopian tube in females.
The main structures of the suprapubic region include the bladder in males and females, and the uterus in females (along with the respective reproductive structures for males and females).
The main structures of the LLQ include the colon (sigmoid/descending) in males and females, and the left ovary/fallopian tube in females.
Lower Abdominal Pain
Now that we have discussed the main structures in each region of the lower abdomen, let’s discuss potential causes of abdominal pain by location.
**Below focuses on the main pathology for each quadrant and is not an extensive list of all abdominal pathology that can occur.
Right Lower Quadrant
The primary structures in the right lower quadrant include the appendix and cecum in both males and females, along with the right ovary and fallopian tube in females.
Therefore, problems with any of these structures may cause right lower quadrant pain.
Pathology to the appendix includes appendicitis, a diagnosis that is often considered with right lower quadrant pain (early appendicitis may start as generalized pain).
Pathology to the cecum may also cause right lower quadrant pain and this could include infection, inflammation (colitis), perforation, obstruction, etc.
Ovarian pathology may include ovarian torsion (twisting of the ovary), ovarian cyst (especially if ruptures), and tubo-ovarian abscess (TOA, abscess involving the ovary/fallopian tube).
Lastly keep in mind those other structures that can extend into the right lower quadrant - small intestine, ascending colon, and right ureter.
Therefore, diagnoses such as a kidney stone in the right ureter, and inflammation/infection of that particular portion of the small intestine or ascending colon extending into the right lower quadrant may also cause discomfort in this location.
Suprapubic
The main structure in the suprapubic region for both males and females is the bladder.
Therefore, problems with the bladder such as cystitis or a urinary tract infection may cause suprapubic pain.
We also said the uterus and associated reproductive structures are located in the suprapubic region in females.
Therefore, pregnancy can cause lower abdominal discomfort, especially if there is an ectopic pregnancy in which the embryo attaches to a location other than the uterus (may also cause right or left lower quadrant pain as well).
Since reproductive structures are located in the suprapubic region, whether male or female, sexually transmitted infections may also cause lower abdominal discomfort.
Pelvic inflammatory disease (PID), which is typically a female complication from sexually transmitted infections, may also cause suprapubic pain.
Lastly, remember portions of the small intestine, right and left ureters, and aorta/iliac arteries may also extend into the suprapubic region.
Problems with these structures may cause suprapubic discomfort as a result (abdominal aortic aneurysm, kidney stones at the ureterovesical junction, inflammation/infection of small intestine, etc).
Left Lower Quadrant
The left lower quadrant primarily contains the sigmoid portion of the colon in both males and females.
Sigmoid pathology may include diverticulitis (inflammation and/or infection of the diverticulum involving the colon - commonly the sigmoid) which can cause left lower quadrant pain.
The left ovary and fallopian tube are also present in this region in females, and similar pathology we discussed above with the right ovary/fallopian tube can also occur in the left.
Lastly, remember portions of the small intestine, descending colon, and left ureter may also extend into the LLQ.
Therefore, problems with these structures may cause discomfort (kidney stone in left ureter, infection/inflammation of descending colon or small intestine, etc).
Image: Potential causes of lower abdominal pain based on location to the right lower quadrant, suprapubic region, and left lower quadrant.
Referred Pain - From the Abdomen
While the source of abdominal pain may come from the organs and structures within that region, referred pain may also be present.
Referred pain is defined as pain that is perceived at a location different from where the stimulus is.
Pain may also radiate - pain that originates in one area and spreads to another in a fairly continual pattern.
Pain may also migrate - pain that originates in one location and then moves to a completely different location.
Here are a couple intra-abdominal examples in which pain can radiate or migrate elsewhere.
Radiating Pain
While kidney stones often cause flank pain, this pain can radiate to the groin/lower abdomen.
In fact, the patient complaint of “flank pain radiating to the groin” is a common buzzword phrase that shows up on medical examinations.
Migratory Pain
Early appendicitis can present as generalized abdominal pain or periumbilical pain. As the disease progresses, the pain usually migrates to the right lower quadrant.
Image: Abdominal pain may radiate (kidney stones: flank pain radiating to the groin) or migrate (appendicitis: early appendicitis causing generalized periumbilical pain and then migrating to RLQ).
Referred Pain - To the Abdomen
Similar to how intra-abdominal pathology can cause referred pain outside the abdomen, pathology outside the abdomen can cause referred pain in the abdomen.
Let’s take a look at some examples.
Lower Abdomen
When pain is referred to the lower abdomen, it could be caused by pathology in the hip or pelvis.
Therefore, problems in the hip or pelvic region can present as lower abdominal discomfort.
For example, hip fractures, osteoarthritis, or musculoskeletal injuries involving the hip/pelvis may lead to referred pain in the lower abdomen.
While the ovaries can cause lower abdominal pain in females as they are directly located within the lower quadrants, testicular pathology can also cause referred pain to the lower abdomen in males (or hip and leg - sometimes seen in pediatric patients) despite their external location.
Testicular pathology may include testicular torsion (twisting of the testicle), orchitis (inflammation and/or infection of testicle), or epididymitis (inflammation and/or infection of the epididymis).
Therefore, it is important to consider testicular pathology in a male presenting with lower abdominal pain.
Image: Sometimes pathology outside the abdomen (hip fractures, testicular torsion, orchitis, etc) may cause referred pain to the lower abdomen.
Conclusion
Hopefully this was a good overview of the lower abdomen including the anatomy and causes of pain.
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