1. Equine Colic: Ultrasonographic and Radiographic Diagnosis
Mattie McMaster and Friends

2. Introduction Colic COLIC ABDOMINAL PAIN
In the wild,
there is no healthcare.
Colic
ABDOMINAL PAIN
Most commonly associated with gastrointestinal abnormalities
Outcome:
Resolve spontaneously
Medical treatment
Surgical treatment
Most common reason for equine emergency treatment
Cause can vary from mild spasmodic colic to life-threatening large colon strangulation
The incidence of colic in the U.S. horse population was estimated to be 4.2 colic events/100 horses per year at an estimated annual cost of $115.3 million to the equine industry. The fatality rate was 11%, and 1.4% of colic events resulted in surgery
COLIC

3. Badness!!!

4. Diagnostic Tools Patient history and signalment Physical exam
CBC, biochemistry and blood-gas
Naso-gastric intubation
Rectal palpation
Abdominocentesis
ULTRASONOGRAPHY
RADIOGRAPHY
Exploratory surgery

5. Ultrasonography
and Radiology

6. Indications Obtain a more specific diagnosis
This is a good day
to save lives…
Obtain a more specific diagnosis
Decide if surgical intervention is necessary
Estimate prognosis
Prognosis for horses with more serious causes of colic has improved dramatically over the past 10 years, predominantly because of early referral and surgical intervention.
Ultrasonography is more sensitive than palpation per rectum for identifying SI distention and can be used to assess the degree of distention, wall thickness, luminal contents, and motility.
Ultrasonographic identification of distended, thickened, amotile SI was 100% sensitive and 100% specific for the presence of a strangulating lesion
Specific causes of colic where ultrasonography has been used to help with obtaining a more definitive diagnosis include nephrosplenic ligament entrapment (NLE), RDD, LCV, intussusception, and peritonitis.

7. Ultrasonography: Equipment+ +
+/- =

8. Preparation Soak abdomen in alcohol Can produce goood images
Time-efficient for emergencies
May have negative impact on some probe surfaces
Abdominal clipping
#40 clipper blades
For older, obese, or thick-coated horses
Preferred for chronic colic over alcohol cases due to subtle ultrasonographic changes
Ventrally the clipped area should extend from the xiphoid to the pubis and laterally to connect with the clip extending ventrally from the paralumbar fossa and intercostal spaces
Wipe the abdomen with a wet sponge to remove debris
Apply ultrasonographic gel

9. Transducer Low frequency transducer Sector transducer
Game-face
Low frequency transducer
Sector transducer
Curvilinear transducer
Machine position
Low frequency transducer
MHz
Sector transducer
Excellent penetration
Curvilinear transducer
Superior resolution to depths of 27-30cm
Place machine near horse’s shoulder to prevent it from being kicked

10. Scan Regions Red circle: Paralumbar and flank region Blue circle:
Intercostal spaces to costochondral junctions
Green circle:
Ventral abdomen from sternum to inguinal region

11. Normal
No surgery?

12. Equine Abdomen Components of the gastrointestinal tract
Stomach, duodenum, small intestine, large colon, small colon, cecum, rectum
Liver, spleen, kidneys

13. Spleen Oh hey. Left Blue line: Ventral lung boarder
Red triangle: Area to clip and visualize the spleen
The spleen can be visualized between the 8th-17th intercostal space or the paralumbar fossa
For the spleen, the ultrasound examination should include the entire left side of the abdomen, beginning at the lung’s ventral most margins and extending ventrally to the ventral midline
In a few normal horses, the cranial pole of the spleen is located in the right cranioventral abdomen in the 6th and 7th intercostal spaces
The most echogenic organ in the abdomen and is normally visualized in the left side of the abdomen, ventral to the lung margins on the abdominal side of the diaphragm from the 7th or 8th intercostal space to the paralumbar fossa
The spleen is recognized by its more granular homogeneous texture with few vessels coursing throughout
Left

14. Stomach
The stomach is usually imaged over 3 to 4 intercostal spaces in the left cranial to mid abdomen and may be detected medial to the spleen from the 9th- 12th ICS or be located more caudally in the abdomen in the 11th-13th ICS.
Appears as a curvilinear echo medial to the spleen and caudal to the liver
If it is filled with gas, reverberation artifact and acoustic shadowing obscure deep portions of the stomach
Gastric wall is hypoechoic to echogenic with a hyperechoic gas echo from the mucosal surface and normally measures from 4 to 7 mm in thickness.
Gastric rugal folds can be often be imaged in adult horses, particularly when they have been held off feed.
Left

15. Kidneys
The left kidney is located slightly more caudally and ventrally in the abdomen.
Right kidney- prepare area between 14th and 17th intercostal spaces on the right side of the abdomen. Prepare along a line that is parallel with the dorsal and ventral aspects of the right tuber coxae
Left kidney: Prepare from the 15th intercostal space to the paralumbar fossa, and from a line level with the left tuber coxae to a line level with the left tuber ischii
Abnormal: Intervening gas-filled bowel may obscure the left kidney when imaging from the transcutaneous approach. Occasionally, intervening gas in the duodenum may also obscure visualization of the right kidney
Left
Right

16. Duodenum
- The duodenum is imaged around the caudal pole of the right kidney and medial to the right liver lobe.
It can be traced orad between the right lobe of the liver and the right dorsal colon to the mid abdomen (11th intercostal space), where it is lost from view. It appears small and circular (when sliced in its short axis) with a hypoechoic to echogenic wall, also 3 to 4 mm in thickness, and has a fluid lumen. The duodenum usually appears partially collapsed and its peristaltic motion is easily visualized during real-time scanning.
Right

17. Small Intestine
Wall of jejunum is hypoechoic to echogenic with a hyperechoic echo from the mucosal surface and is usually 3 mm or less in thickness.
The ileum, is slightly thicker (4–5 mm).
Small intestine is generally flaccid, characterized by little or transiently visible lumen contents, and usually has rhythmic contractions. Some anechoic fluid and hyperechoic gas is often imaged in the lumen of the jejunum.
Because of the poorly developed large colon in neonatal foals, sonographic evaluation of a large portion of the small intestine is possible. In foals older than 4 months of age, sonographic visualization of the small intestine is limited to the inguinal region
Left

18. Large Intestine Left Right
Large intestinal echoes are usually imaged in the intercostal spaces (ICS) and the flank.
Recognized by their large semicurved, sacculated appearance, except for the right dorsal colon.
The large intestinal wall is hypoechoic to echogenic with a hyperechoic gas echo from the mucosal surface and normally approximately 3 mm in thickness.
The right dorsal colon has a smoother non-sacculated appearance and is most consistently imaged from the right 11th-13th intercostal spaces, but can be imaged in the right 10th and 14th intercostal spaces as well. Normal wall thickness of 3.3 to 3.5 mm have been reported for the right dorsal colon.
Thickness of the right ventral colon measured at the 12th intercostal space is approx. 3.6 mm
Peristaltic activity is normally visualized.
Left
Right

19. That’s what
she said.
Cecum
Right

20. Scan Patterns Three patterns Evaluate Mucous Fluid Gas Wall thickness
Mmmmm,
scan patterns.
Three patterns
Mucous
Fluid
Gas
Evaluate
Wall thickness
Layering
Uniformity
Luminal Contents
Peristalsis
Three sonographic patterns of the luminal contents of the bowel have been described: mucous, fluid, and gas. Collapsed bowel that contains a hyperechoic lumen without distal acoustic shadowing represents the mucous pattern with mucous and trapped gas in the lumen of the bowel. Echoic to hyperechoic luminal contents with clean or dirty distal acoustic shadowing is the gas pattern. Anechoic luminal contents are imaged with the fluid pattern.
One should evaluate bowel wall thickness and layering, uniformity in bowel diameter, luminal contents, and peristalsis. If disease is present, one should determine whether the disease is focal or generalized and which portion of the gastrointestinal tract is affected.

21. Through concentration,
Abnormal
Through concentration,
I can raise and lower
my cholesterol at will.

22. Medical Colic Enteritis/ duodenitis Right dorsal colitis
Brilliant diagnosis.
Enteritis/ duodenitis
Right dorsal colitis
Verminous arteritis
Gastric distension
Gastric ulceration
Gastric SCC
Intestinal neoplasia
Abdominal abscess
Peritonitis

23. Enteritis/ Duodenitis
Fluid distension of intestinal tract with increased peristalsis
Developing enteritis
Wall thickened, edematous and more hypoechoic
Shreds of intestinal mucosa in lumen
Marked fluid distension of stomach
Enterocolitis more common in neonates
While in many cases the cause is unknown, infection with Clostridium spp and Salmonella spp has been reported in cases of colitis
The challenge is differentiating a horse with colitis from a horse with a surgical lesion. While there is no definitive diagnostic test to differentiate between these types of lesions; anecdotally, dullness, fever, leukopenia, and yellow-to-orange peritoneal fluid with a very a high total protein concentration (>4 g/dL) and a normal nucleated cell count are more likely associated colitis than with a surgical lesion.
- The lack of motility in these intestinal segments is consistent with an ileus, and the thickness and echogenicity of the bowel wall are an indication of the degree of involvement of the bowel wall
Adults with proximal duodenitis/ anterior enteritis may have an associated cholangiohepatitis with elevated biliary enzymes.
Figure 1- Sonogram of the right side of the abdomen obtained from the right 15th intercostal space in a horse with duodenitis. Notice the distention of the duodenum with fluid (arrow) and the mild thickening of the duodenal wall (0.55 cm). There is some slight settling of the ingesta in the most ventral portion of the duodenum. The duodenum was very hypomotile in real time. Dorsal is to the right and ventral is to the left
Figure 1

24. Duodenitis
- Figure 2- Duodenitis in a 7-year-old Peruvian Paso gelding with a several month history of colic. The duodenum was hypomotile with a wall thickness of 5-8mm. The horse was treated with diet modification and anti-ulcer medication. 30 day recheck ultrasound revealed resolution of the duodenitis. Image obtained from the right 13th ICS at a scanning depth of 14.6cm.
Figure 2

25. Right Dorsal Colitis Non-steroidal anti-inflammatory drug toxicity
Thickened right dorsal colon
Ventral to liver in right 10th-14th intercostal spaces
- Figure 1- Sonogram of the right dorsal colon obtained in the 15th intercostal space in a horse with right dorsal colitis. Notice the marked thickening of the wall of the right dorsal colon (arrow) to just over 2 cm. There is an increased amount of anechoic peritoneal fluid visible in this sonogram. Dorsal is to the right and ventral is to the left.
Figure 3

26. Gastric Distension Stomach is enlarged and filled with fluid
Hyperechoic ventral layer representing ingesta
Hyperechoic dorsal layer casting dirty shadows consistent with gas
Gastric impaction is a markedly enlarged gastric echo extending over five or more intercostal spaces on the left side of the abdomen. The stomach is usually slightly less circular than normal, with hyperechoic material casting an acoustic shadow in the lumen of the stomach.
Figure 1- Sonogram of the stomach obtained from the left 12th intercostal space from a horse with gastric distention. Notice the layering of the gastric echo with the hyperechoic gas located dorsally (right arrow) and the small amount of echoic ingesta located ventrally (left arrow). The fluid ventral to the dorsal gas cap contains small hyperechoic echoes representing gas mixed in with the fluid. The black shadow between the dorsal gas cap and the ventral ingesta is a shadow from the indwelling nasogastric tube. Dorsal is to the right and ventral is to the left.
Figure 4

27. Intestinal Neoplasia
Not routinely visualized on transcutaneous ultrasound
Lymphosarcoma
Within intestinal wall
Diffuse irregular filling
Marked enlargement of mesenteric lymph nodes
- Could potentially used transrectal ultrasound
- Figure 2:Severe annular thickening of the small intestine in a 20-year-old Miniature Horse with a 2 year history of intermittent colic. The muscular layer (arrows) is markedly thickened (8-13mm) with associated mucosal/submucosal thickening. GI motility was severely reduced. The horse’s attitude and clinical signs improved markedly following surgical resection of 15 feet of SI. Histology confirmed idiopathic muscular hypertrophy.
Figure 5

28. Abdominal Abscess Figure 6 Found: Fluid-filled or solid
Ventral abdomen
Root of mesentery
Cecum
Large colon
Fluid-filled or solid
Movement of adjacent bowel should be examined:
Adhesions between adjacent intestine and abscess
Figure 1- Transrectal sonogram of a horse with an abdominal abscess at the mesenteric root. Notice the hypoechoic loculated fluid structure with the echoic center consistent with an abscess (arrows).
Figure 6

29. Peritonitis Ventral abdomen Evaluate fluid: Evaluate:
6.0 to 10.0 MHz transducer
Evaluate fluid:
Relative quantity
Character
Evaluate:
Abdomen, gastrointestinal and abdominal viscera should be scanned for source of peritonitis
Abdominal abscess or devitalized bowel
Large amount of fluid- use a a 5.0 MHz or lower frequency transducer
Character- hypoechoic, swirling, homogeneous fluid or echogenic, flocculent, composite fluid, fibrin, and/or adhesions
The detection of hypoechoic or echogenic, flocculent, composite fluid, fibrin, and/or adhesions between the serosal surfaces of the intestine and the abdominal wall is compatible with peritonitis.
Free gas echoes and/or particulate echogenic debris are consistent with a ruptured viscus
Homogeneous, hypoechoic to echogenic cellular fluid is imaged with hemoperitoneum, which is usually distinguished from septic fluid by the detection of swirling fluid, associated with movement of the gastrointestinal viscera and respiration and the settling and stirring of blood components. The kidneys, liver, and spleen should be carefully examined in adults with hemoperitoneum to determine whether these organs are the cause of the hemorrhage.
Figure 1- Sonograms of the ventral abdomen obtained from a horse with peritonitis and a devitalized leaking small intestinal wall. The peritoneal fluid is very echoic with a small loculated accumulation of fibrin associated with the jejunal mesentery (large arrow). Hyperechoic pinpoint echoes representing gas (small arrows) are present on the serosal surface of a very thickened loop of jejunum, indicating leakage of intestinal contents through the bowel wall.
Figure 2- Sonogram of the ventral abdomen obtained from a horse with a hemoperitoneum. Notice the large amount of swirling hypoechoic fluid in the peritoneal cavity. The normal large colon is floating on this hemorrhagic fluid. Cranial is to the right and caudal is to the left.

30. Surgical Colic Herniation/ displacement
Let’s have
some fun….
Herniation/ displacement
Nephrosplenic ligament entrapment
Sand colic/ enterolithiasis
Intussusceptions
Large colon torsion
Strangulating small intestinal and small colon lesions
Small intestine masses
Impaction

31. Herniation/ Displacement
Abnormal position of gastrointestinal viscera difficult to diagnose
Exceptions:
Scrotum
Thoracic cavity
Umbilical hernia
Abnormal position difficult to diagnose unless it is displaced in the scrotum, thoracic cavity or there is an umbilical hernia
Right dorsal displacement of the LC more likely to occur in horses 4 to 10 years of age and wider-bodied horses like Quarter Horses. Typically see the LC becoming displaced between the cecum and the right body wall
Displacements of the LC include RDD and left dorsal displacement (LDD) or NLE. Other displacements, such as pelvic flexure retroflexion, can also occur and are likely a form of the more commonly reported displacements
Figure 1- Sonogram of the left ventral abdominal wall obtained from a horse with an abdominal wall hernia. Notice the loop of small intestine (arrow) trapped between two layers of the abdominal wall near the edge of the hernia, where it was only a partial thickness hernia. Dorsal is to the right and ventral is to the left.
Figure 9

32. Nephrosplenic Ligament Entrapment
Dorsal spleen and left kidney not visible in left caudal abdomen
Visualize ingesta or gas-filled large bowel
Spleen ventrally displaced
Bright hyperechoic reflection dorsal to the spleen from the bowel
- The sonogram can be used to see if treatment with phenylephrine, followed by lunging, or rolling the horse has successfully corrected the nephrosplenic ligament entrapment
- Figure 1- Sonogram of left abdomen obtained from the 14th intercostal space from a horse with a nephrosplenic ligament displacement. Notice the horizontal dorsal border of the spleen with the hyperechoic large colon located dorsal to the spleen (arrow). The spleen is ventrally displaced throughout the left side of the abdomen. Dorsal is to the right and ventral is to the left.
Figure 10

33. Sand Colic/ Enterolithiasis
RADIOGRAPHS
Not often used in adult horses
Exceptions:
Sand Colic
Enteroliths
Sandy regions, such as California, Arizona, Colorado, Michigan, Florida, and New Jersey
Radiology is not often used as a diagnostic modality for adult horses with colic. However, radiography can be useful for diagnosing the presence of enteroliths and sand in adult horses.
Figure 11

34. Enterolithiasis
Figure 12

35. Sand Colic Small, pinpoint granular hyperechoic echoes
Multiple acoustic shadows
Ventral most portion of the affected intestine
Limits peristaltic movement
Like enterolithasis, the sand weighs down the affected intestine, and the affected intestine is best visualized in the ventral abdomen
Repeated ultrasonographic examinations can be performed to monitor the resolution of the sand impaction

36. Enterolithiasis Enteroliths, bezoars, fecaliths, Hasselhoffs
Affected bowel in ventral abdomen
Hyperechoic mass casting strong acoustic shadow within intestine lumen
Distension of intestine proximal
Oh hey..
- Horses from California are predisposed to enterolithiasis
- Fecaliths occur commonly in Miniature horses at the level of the small colon
- Make the bowel much heavier than normal, causing it to fall to the floor of the ventral abdomen
Figure 13: Badness.

37. Intussusceptions Ileum and large bowel Right side of abdomen
“Target sign”
Fibrin tags between segments of intestine
Most common in neonates
There are many different possible sonographic appearances for the intussusception, depending on which portion of the intussusception is being imaged. With large bowel intussusceptions, the intussuscipiens has a markedly thickened, puckered, or sacculated appearance with multifocal echoic areas in an otherwise hypoechoic wall.
Sonogram of the right side of the abdomen obtained from a horse with a cecal intussusception. Notice the thickened outer loop (intussuscipiens) and the thick small apex of the cecum (intussusceptum) with a small layer of fluid in between the two portions of the cecum creating a target or bull’s eye sign. Dorsal is to the right and ventral is to the left.
Figure 14

38. Intussusceptions Figure 15
- Figure 14: Colocolic intussusception visible from the right 11-13th ICS in a 17-year-old Tennessee Walking horse with a 2 week history of mild colic symptoms. The edematous intussuscipiens (arrowheads) surrounds the more echogenic intussusceptum (arrow). The intussusception could not be reduced at surgery, and the horse was euthanized.
Figure 15

39. Large Colon Torsion Increased wall thickness of the large colon
Increased wall thickness is diffusely hypoechoic
Badness!
LCV is a rapidly life-threatening lesion and requires the most immediate attention for a favorable outcome
Broodmares are commonly affected by LC volvulus at 1 to 3 months postfoaling
This increased wall thickness is diffusely hypoechoic and occurs with a loss of the normal layering of the wall of the gastrointestinal tract.
A colon wall thickness of ｳ9 mm obtained from a ventral abdominal window accurately predicted that large colon torsion was present in 8 of 12 horses.
Figure 1- Sonogram of the left ventral abdomen obtained from a horse with a large colon volvulus. Notice the thickening of the colonic wall (arrow) and the increased amount of peritoneal fluid. Dorsal is to the right and ventral is to the left.
Figure 16

40. Strangulating Small Intestinal Lesions
Distended, fluid-filled small intestine proximal to strangulated portion of small intestine
Strangulated small intestine
Thickened, edematous, hypoechoic walls
Little or no peristaltic activity
Ventral portion of abdomen
May be associated with a lipoma or epiploic foramen entrapment
Amotile edematous loops of small intestine have been imaged in the right side of the abdomen in horses with epiploic foramen entrapment of the small intestine
Mucosal thickening of the wall of the strangulated loops of small intestine is usually less echoic than wall thickening associated with cellular infiltration, fibrosis, or hypertrophy of the intestinal wall, usually seen in non-strangulating lesions
Sloughing of the intestinal mucosa may occur in association with an anechoic fluid line in the underlying layer. Gas echoes may also be imaged within the wall of the intestine in horses with intestinal necrosis
Figure 1: Small intestinal obstruction with secondary small intestine dilation
Figure 17

41. Small Intestinal Masses
Within intestinal wall
Thickened wall
Anechoic to echogenic
Carcinoids, leiomyomas, granulomas, hematomas, and fibrosis
Stricture secondary to chronic colic
Intestinal obstruction
Within lumen
Hemorrhage appears as echogenic clots or echoic swirling fluid
Intramural hemorrhage appears as anechoic loculated fluid in the wall of the small intestine, whereas intestinal tumors, granulomas, and fibrosis all have a more solid, echoic sonographic appearance
Figure 3: Intraluminal small intestinal mass in a 20-year-old Arabian mare with a 2 year history of recurrent colic. Distention is seen proximal to the mass (arrow) with an increased wall thickness (9-10mm). The mass was located in the cranioventral abdomen and extended for a length of 15cm. The owner refused surgical intervention, and the horse was lost to follow-up.
Figure 18

42. Impaction Round to oval distended viscus Lack visible sacculations
Wall normal to increased thickness
Large acoustic shadows from impacted ingesta
Distension of intestine proximal
Little to no motility
Impactions of the pelvic flexure (left ventral colon), right dorsal colon, and SC occur commonly. In addition, there are cecal impactions
More common in older horses due to poor dentition
Meconium impactions occur in neonates
- Only be imaged sonographically when the impacted portion of the large colon or cecum is adjacent to the body wall or fluid is interposed between the affected portion of the intestine and the body wall.
Figure 19

43. Conclusion
Early referral and surgical intervention is key to successful outcome
Ultrasonography and Radiology:
Obtain a more specific diagnosis
Decide if surgical intervention is necessary
Estimate prognosis

44. QUESTIONS?