Mr Lim used to sell chicken rice.
His shop was close to where I used to work. “I know that place!” I exclaimed. His face lit up. A stout man in his fifties, he had a been to another hospital with abdominal pain and diarrhoea for 4 days. The pain first began in the upper part centrally, then moved to the lower right part of the abdomen. An ultrasound scan was reported to show acute appendicitis.
Surgical textbooks would have us believe this is a perfect description of pain due to appendicitis. He was markedly tender in the lower right quadrant and he had a fever.
“We should do a CT scan of your tummy, just to make sure it’s really appendicitis.”
Experience had taught me things are not always what they seem to be.
A CT scan gives far clearer images of the abdomen than an ultrasound scan.
CT scans vs Ultrasound scans
CT scans or computerised tomography scans use X-Rays. Many X-ray images are taken rapidly from different directions.
A computer then combines all the images and reconstructs them as slices, rather like sliced bread.
Nowadays, CT scanners are very fast and accurate.
They do involve a little bit of exposure to X-rays (though not a high dose).
The other downside to CT scans is that they require an injection of intravenous contrast to get clear meaningful images. Some patients are allergic to iv contrast. In addition, iv contrast can also affect kidney function and care will have to be taken in patients with impaired kidney function.
Nevertheless, CT scans are well tolerated by the vast majority of patients and the invaluable information they yield often outweigh the downsides.
Ultrasound scans on the other hand use very high pitched sound waves to create the image. These sound waves are too high pitched for us to hear. The sound bounces off various tissues and are picked up by the ultrasound probe listening for echoes, rather like radar.
Ultrasound is good, fast, painless, cheap and safe.
It is the safest way to look at babies in the womb, for instance.
To have an ultrasound scan, the doctor has to cover the abdomen with jelly.
Ultrasound is great for finding out if a lump is made of tissue (solid) or fluid (cystic). Ultrasound can demonstrate blood flow in a simpler way than CT scans. They are also cheaper than CT scans.
However, ultrasound does not pass through air or bone. If there is bowel (containing air) in the way, that will block the ultrasound, limiting what can be seen. The same goes for bone. Ultrasound is generally not good at looking at the bowel.
The resolution of ultrasound depends on the frequency of the probe used. Higher frequencies give clearer images and more detail but have more limited penetration. Lower frequencies for deeper structures have lower resolution. This means deeper tissues are better imaged with a CT scan.
In summary, CT scans and ultrasound use very different technologies to create the image. They are best viewed as complimentary – some things are better seen on CT and others on ultrasound. We doctors like to have the best of all possible worlds so that’s why we have both!
Sure enough, the CT showed the appendix to be enlarged and distended, as one would expect for appendicitis.
Except ……….. the wall of the appendix was not thickened or inflammed. Nearby, there was plenty of inflammation, mostly centered on the large bowel next to the appendix. Indeed, there was even a small pocket of air outside the bowel indicating perforation.
Mr Lim had a perforation of the large bowel, not appendicitis as initially suspected.
In the absence of trauma or injury, the most likely cause was Diverticular Disease.
Diverticular Disease – What is it?
A diverticulum is a small pouch or pocket in the wall of the bowel. In diverticular disease, there are many such pouches or diverticula. This is a benign condition and has no association with cancer. Many patients with diverticular disease have no symtoms and may not even be aware they have the condition unless they have a colonoscopy. However, some patients develop complications which can sometimes be severe or life threatening (see below).
Diverticular disease is thought to result from constipation.
The large bowel (colon) is a muscular tube made up of different layers. On the inside of the tube is the mucosa, a thin layer like tissue paper.
With prolonged constipation and straining, pressure builds up inside the bowel as it tries to propel the faeces onwards. Weak spots develop in the muscle wall causing small holes to form. The inside mucosa pouts out through these holes in the muscle to form little pockets or diverticula.
An important aspect of these diverticula is that they are very thin walled, lacking a muscle coat.
It is not hard to imagine these diverticula bursting when inflammed, leading to a perforation of the bowel.
Indeed, it can even be a hazard while doing a colonoscopy as it is possible to cause a perforation with the scope. Fortunately, this does not happen often.
It is for this reason I am always very careful when performing a colonoscopy on patients with diverticular disease.
Sometimes, one can treat small perforations due to diverticular disease with intravenous antibiotics. The perforation is sealed off by fat and the infection slowly resolves.
However, I was worried about Mr Lim.
He had diabetes as well and diabetic patients generally have a lower resistance to infection such as one would get with a perforated large bowel diverticulum. If the perforation got bigger instead of sealing off, he could get worse leading to an abscess. Moreover, persistent infection would make his diabetes more difficult to control.
Better to get it properly sorted out.
That meant removing the affected part of the large bowel then joining it all up again.
A much bigger operation than appendicectomy.
a bigger operation… through the same small holes!
So we proceeded to bowel resection after carefully bringing his diabetes under control.
All done with keyhole (laparoscopic) surgery.
Mr Lim made a great recovery and the results from the lab confirmed our suspicion of a perforated diverticulum.
Complications of Diverticular Disease
Most cases of diverticular disease do not cause any trouble and patients are often unaware they have thin condition unless they have a colonoscopy or CT scan. Some cases do go on to develop complications which can be severe.
The main complications are:
This occurs when a lump of faeces gets stuck inside a diverticulum. That diverticulum can get obstructed and inflammed. The inflammatory mass can look like cancer even though it is benign. The patient complains of fever and a tender hard mass in the abdomen.
The diverticulum often has a blood vessel running inside and inflammation can lead to bleeding. This bleeding can sometimes be severe, requiring emergency surgery. Diverticular disease is the commonest cause of massive fresh rectal bleeding.
If the inflammation in the diverticulum progresses, it can lead to perforation, as in this case. Untreated, the leakage of faeces causes infection which can lead to septic shock. The body tries to wall off the leak and this can result in an abscess. The patient has a fever, tender mass and may experience a change in the bowel habit.