Normal findings in the post abdominal surgery (Figs 1 and 2)
After surgery there are findings that we can consider as postsurgical normal changes.
They may be related or not with the patient's clinical and are often difficult to distinguish from pathology.
Pneumoperitoneum
It is the presence of air within the peritoneal cavity.
This finding is usually considered abnormal and indicative of bowel perforation.
Nevertheless,
it is considered normal in some contexts as surgery,
since it involves opening of this cavity.
● In the case of laparotomy,
the peritoneum is cut and the peritoneal cavity is exposed in the operating room.
● In the case of laparoscopic surgery,
CO2 is introduced at a pressure between 12 and 15 millimeters of mercury within the peritoneal cavity.
Although this is a normal finding after surgery,
a complication should be suspected if it is present beyond 7 days after surgery.
In these cases,
having two imaging studies performed at different days may help clarify whether it is pneumoperitoneum in connection with surgery or may be caused by bowel perforation.
● Surgical pneumoperitoneum tends to decrease over the days after surgery.
● Progressively increasing pneumoperitoneum leads to suspect serious surgical complication like perforation or wound dehiscence.
● Regardless of imaging findings,
clinical progression of the patient is also important to differentiate these two entities.
In the surgical pneumoperitoneum,
in absence of other complications,
patient clinical status should progress favorably.
However,
if bowel perforation or wound dehiscence are present,
patient should be progressively worse because of chemical or bacterial peritonitis.
Small amounts of liquid
Small amounts are normal and they have no clinical significance.
Fluid retention is usually caused by hypoproteinemia,
fluid overload,
cardiac or renal comorbidities.
Basal atelectasis
Pleural effusion and increased intraabdominal pressure lead to formation of atelectasis.
They can become infected.
Extraperitoneal gas
The high pressure of laparoscopic gas during these procedures can lead to the extensión of this air into the preperitoneal space,
specially on superficial layers.
Air bubbles may enter the subcutaneous tissue reaching the chest or even the neck.
Surgical materials.
Staples,
metal sutures,
catheters ...
should be correlated with the surgical procedure.
Retained foreign materials lead to the formation of adhesions,
fibrosis,
fistulas and infections.
Pathological findings in the postsurgical abdomen
Hematoma of the wall
It is common to find wall hematomas because of damage caused by the introduction of the trocar.
Typically,
hematomas occur as a result of lesions in small vessels at the site of surgical access.
The hematoma occurs when removing trocars (usually within the first hour) because the fact of keeping in place can plug the bleeding.
Atmospheric pressure caused by the surgical pneumoperitoneum also contributes to vessel closure.
Hematomas have the following image presentation:
In Doppler ultrasound,
they appear as heterogeneous echogenicity lesions with liquid content formed by coagulated blood and debris.
Using this technique,
it is not possible to directly demonstrate active bleeding.
If an increase in size in comparison with a previous ultrasonography occurs,
there is a high probability of active bleeding.
In those cases a tomographic angiography must be performed in order to confirm the finding and locate the bleeding vessel.
CT angiography can characterize the hematoma.
On one hand,
it allows accurate measurements,
assessment of deep levels.
If active bleeding is suspected,
a three phase protocol can be performed:
● Empty phase,
without intravenous contrast,
to assess baseline density of the different structures.
● Early arterial phase allows assessment of the integrity of arteries and evaluation of the presence of contrast leakage.
Contrast extravasation involves active bleeding and vessel rupture.
● Venous phase,
allows the assessment of possible venous bleeding or low flow arterial bleeding,
which has not been seen in the arterial phase.
If the size of the hematoma remains stable and no active bleeding is observed,
the patient receives a conservative management.
If there is active bleeding,
vascular intervention should be performed.
Surgical wound infection (Fig 3):
It is a high morbidity lesion (between 60- 80% of all postsurgical infections) and usually appear around the fifth day.
They are classified as:
- Superficial,
if it is limited to subcutaneous tissue.
- Deep,
if it reaches fascial planes and muscles.
The importance of the radiology report is the identification of collections susceptible to receive drainage or antibiotic treatment.
Complications of surgical anastomosis: Dehiscence / suture leakage (Figs 4,
5 and 6):
It is defined as the loss of contact of the surgical margins with partial opening of the suture.
It is the most feared complication because of its high mortality (approximately 50%) if not quickly identified and treated.
It usually appears between 5th and 7th day.
The evolution to peritonitis,
fistula and abscess is quick if not detected early.
There are a number of predisposing factors: age,
technical difficulty and location,
being more frequent in surgery below the peritoneal reflection (rectal surgery).
According to their importance and therapeutic management,
they are classified as:
● Minor leak: leakage or perianastomotic collection which does not require therapeutic maneuvers (percutaneous drainage or reoperation).
● Major leak: perianastomotic presence of leakage or collection that needs invasive therapeutic maneuvers (percutaneous drainage or reoperation).
Radiologic diagnosis: CT.
● Collections and leaks can be assessed.
● Identification of free liquid,
perianastomotic collections or pneumoperitoneum.
Vascular complications: Bleeding (Figs 7 and 8).
It is rare,
but it can become serious.
● Intraluminal.
It is characterized by hematemesis or melena.
● Extraluminal - intraabdominal.
It is suspected because of decrease of the hematocrit.
○ Early bleeding: first 24 h.
Usually consequence of failure of surgical techniques,
hemostasis or coagulation disorders,
splenic injury.
Treatment: SURGICAL REVIEW and / or delayed embolization.
○ Delayed bleeding.
Caused by a major injury in the clinical setting of residual infection that produces erosion of a vessel (pseudoaneurysm).
Treatment: arteriography embolization.
Radiologic diagnosis: CT.
● In 98% of cases it is possible to identify the cause and plan the possible approach: surgical or interventional.
● Collections with homogeneous,
heterogeneous or hyperdense level (sedimented erythrocytes).
● Attenuation values of liquid of approximately 60 UH on without contrast phase indicate recent bleeding.
Attenuation values decrease as time passes.
● Presence of extravasation characterized by focal collection or visible "jet" on the arterial phase and / or portal vein.
Intestinal: Paralytic ileus (Fig 9)
It is the decrease or absence of peristalsis.
It is a normal phenomenon in postoperative surgery.
It is a disorder that resolves on a limited time:
Stomach: 24-48 h.
Small Intestine 24 h.
Colon: 3 to 5 days.
The diagnosis is based on clinical symptoms.
Prolonged ileus is considered when the absence of peristalsis persists more than 5 days despite conservative treatment.
Radiologic diagnosis: CT.
● Retention of large amount of gas and liquid,
being bowel loops uniformly dilated and affecting both small and large bowel (with distal presence of gas).
● Presence of fluid levels along all intestinal segments on standing position and lateral position projections.
Intestinal: Intestinal obstruction.
Bowel dilatation is produced as a consequence of mechanical obstruction that causes complete and persistent stopping of the intestinal contents at one point.
Causes change over time.
In the immediate postoperative period closed loop obstruction,
volvulus and ischemia should be suspected.
From three weeks after surgery,
the first cause are surgical adhesions.
Radiologic diagnosis: CT
● Dilated proximal and distal bowel collapse.
● Impact of foreign material in the lumen of the bowel.
● Fluid levels in dilated loops.
● Swirl signs: consists of a pseudomass formed by vessels,
fat and loops.
It is the characteristic radiological sign of torsion and volvulus.
Intraabdominal collections (Figs 10 and 11)
There are different types of abdominal postsurgical collections.
● Seroma. This is a collection of sterile liquid.
Usually it considered a physiological finding and they resolve spontaneously.
They can lead to the formation of an abscess.
● Hematoma. Blood collection.
Often they have heterogeneous radiographic density to present different developmental stages in blood or clots inside.
● Abscess. Purulent.
Require drainage by interventional procedures.
● Biloma. Bile fluid collection.
They can become infected and produce an abscess.
Radiologic diagnosis: CT
● It allows to characterize and establish the surgical approach.
● They are low density collections (20 UH).
● Abscesses have peripheral enhancement and gas bubbles inside.
Pathological foreign bodies (gossypiboma)
It is surgical gauze forgotten in a body cavity during surgery.
If they stay some days in the peritoneal cavity,
they can produce a foreign body reaction and form an abscess.
For easy identification,
they usually have a metallic rim that makes identification easy on plain radiography and tomography.