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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • Hernias are abdominal wall defects through which fluid or GI contents can pass depending on the size
  • Umbilical hernias are defects at the site of the umbilicus after umbilical structures regress
  • Inguinal hernias are defects where intestines traverse through the inguinal rings or rupture through the adjacent peritoneum
  • Simple/reducible hernias indicate contents can be pushed back into abdomen
  • Complicated/nonreducible hernias indicate herniated tissue is incarcerated with potential strangulation of associated blood supply and emergency surgery is necessary

Pathophysiology!!navigator!!

Umbilical

  • Umbilical hernias are the most common type of abdominal hernia in the horse
  • The linea alba is discontinuous at birth, but the umbilical ring normally closes within the first few days of life by a fibrous plate
  • Failure of this closure leads to herniation
  • Small (<5 cm) hernias usually close within a few weeks
  • Large defects (>10 cm) or those persisting at the age of 4 months warrant surgical correction

Inguinal

  • Usually unilateral
  • Direct inguinal hernias result from weakness of the transverse fascia adjacent to the inguinal rings, resulting in diverticulum of the peritoneum and associated bowel, and are reported in humans but not equids
  • Indirect inguinal hernias result from GI contents penetrating the vaginal tunic; if contents pass through the internal and external rings into the scrotum the term scrotal hernia may be used
  • Ruptured inguinal hernias occur when the vaginal tunic or peritoneum tears, resulting in bowel traveling subcutaneously

Systems Affected!!navigator!!

GI

  • Small intestine most often herniates through an umbilical or inguinal hernia. Omentum, bladder, small colon, and large colon herniations are also reported
  • The entire loop of small intestines may become incarcerated and strangulated, necessitating resection
  • If only 1 wall of a viscus becomes incarcerated, it may become necrotic and develop into a Richter's hernia

Reproductive

In the case of inguinal hernias, the testicle on the affected side, and sometimes the adjacent testicle, usually becomes compromised enough to necessitate castration (unilateral or bilateral) due to pressure on the testicular blood supply caused by pressure of incarcerated viscera on the spermatic cord.

Skin

Integument is usually healthy and resection of loose skin associated with herniorrhaphy is for cosmetic benefit only. In rare cases the skin may become irritated to the point of sloughing with pathologic hernias, particularly direct or ruptured scrotal hernias.

Urologic

Herniation of the urinary bladder has been reported.

Genetics!!navigator!!

Umbilical

May have a genetic predisposition (see Breed Predilections).

Inguinal

Some breeds overrepresented (see Breed Predilections).

Incidence/Prevalence!!navigator!!

Umbilical

0.5–2% incidence with only 4% progression to incarcerated bowel.

Geographic Distribution!!navigator!!

N/A

Signalment!!navigator!!

Breed Predilections

Umbilical

Any, but some suggestion that Warmbloods and Friesians are overrepresented.

Inguinal

Any, but Standardbreds, American Saddlebreds, Tennessee Walking Horses, and draft breeds are overrepresented.

Mean Age and Range

Simple, congenital hernias <10 cm (umbilical) or indirect (scrotal) may resolve with age. Surgical fixation is recommended for simple hernias that persist past the age of 4 months.

Predominant Sex

Umbilical

Any gender.

Inguinal

Almost exclusively in colts, although cases of geldings and mares exist.

Signs!!navigator!!

General Comments

Signs differ significantly when a simple hernia becomes irreducible.

Historical Findings, Physical Examination Findings

  • Soft, fluctuant swelling that is completely reducible in a nonpainful animal is indicative of a simple hernia
  • Complicated hernias involve incarceration of bowel, resulting in abdominal discomfort
  • Swollen, firm, warm, and painful hernia sac—typical signs when incarceration is present
  • Inguinal hernias often have swelling and peristaltic activity visible in the bowel under the skin if peritoneum and/or vaginal tunic is ruptured

Causes, Risk Factors!!navigator!!

Umbilical

Increased abdominal pressure at birth, umbilical infection, umbilical trauma especially during parturition, excessive straining due to abdominal discomfort.

Inguinal

  • Excessive pressure during parturition may predispose to inguinal hernia
  • Enlarged inguinal rings in some breeds have been proposed as a risk factor

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Umbilical

Omphalophlebitis—often accompanied by signs of systemic illness (fever, lethargy, leukocytosis), thickened and warm umbilicus on palpation, and abnormally large umbilical remnants on US.

Inguinal

Swelling due to trauma or other testicular pathology.

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

N/A

Imaging!!navigator!!

US

Umbilical

  • US allows evaluation of the hernia size and contents
  • Abdominal US can identify secondarily distended intestines or enlarged umbilical structures consistent with omphalophlebitis

Inguinal

US may be beneficial in confirming abdominal structures involved.

Other Diagnostic Procedures!!navigator!!

Abdominocentesis

Serohemorrhagic peritoneal fluid with a lactate consistently higher than peripheral l -lactate is consistent with ischemic bowel, potentially secondary to an incarcerated hernia.

Pathologic Findings!!navigator!!

N/A

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care, Nursing Care!!navigator!!

  • Daily monitoring of the hernia for reduction and comfort of the patient must be mandated
  • Hernia clamps are successfully used by some practitioners in cases of small, simple umbilical hernias, but intestines may become entrapped by the band
  • A figure-of-eight bandage is recommended for colts with reducible nonruptured inguinal hernias until resolution

Activity!!navigator!!

Umbilical

Activity does not need to be restricted as long as daily monitoring can be achieved.

Inguinal

Stall rest or controlled exercise is recommended if a figure-of-eight bandage is applied.

Diet!!navigator!!

N/A

Client Education!!navigator!!

Ensure clients monitor daily for reducibility of the hernia.

Surgical Considerations!!navigator!!

Umbilical

Surgery should be considered if the hernia is >10 cm in size or does not resolve by 4 months of age. A closed or open (resection of the umbilical sac) approach may be utilized.

Inguinal

  • In cases of reducible nonruptured inguinal hernias, resolution may be obtained with castration of the affected side and transfixation ligature of the vaginal tunic and/or closure of the external inguinal ring. Bilateral castration should be performed if the owner does not want to use the animal for breeding, as herniation may occur bilaterally
  • Laparoscopic herniorrhaphy of the internal inguinal ring with preservation of the spermatic cord may be performed when owners want to retain the animal for breeding. Good results have been obtained using either staples, suture, or peritoneal flap with careful closure of the caudomedial aspect of the ring
  • Nonreducible hernias, either umbilical or inguinal, require emergency surgery for correction and potentially resection of affected bowel if strangulated

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • No drug therapy needed for nonsurgical hernias
  • Perioperative antibiotics may be used as a prophylactic measure, especially if strangulated bowel is suspected

Contraindications!!navigator!!

None

Precautions!!navigator!!

None

Possible Interactions!!navigator!!

None

Alternative Drugs!!navigator!!

None

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

Umbilical

  • Simple, small umbilical hernias should be evaluated on a daily basis until the ring is closed in order to allow early recognition of changes in size or consistency of the umbilical sac
  • If colic occurs, consider the hernia as a possible cause

Inguinal

  • Also monitor and reduce daily
  • If colic occurs, consider hernia as a possible cause

Prevention/Avoidance!!navigator!!

A figure-of-eight bandage may help resolve nonruptured indirect inguinal hernia.

Possible Complications!!navigator!!

The most common complication in both hernias is colic and entrapment of bowel.

Expected Course and Prognosis!!navigator!!

Most foals with small umbilical or inguinal hernias have a good prognosis for resolution within the first few weeks to months of life. Larger hernias may not resolve without surgery

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Umbilical

Omphalophlebitis

Age-Related Factors!!navigator!!

Hernias that persist past the age of 4 months are unlikely to resolve without surgical treatment.

Zoonotic Potential!!navigator!!

None

Pregnancy/Fertility/Breeding!!navigator!!

Inguinal

Laparoscopic closure of the internal inguinal rings is required for closure of the inguinal canal if the animal is to retain the testicle on the affected side. Bilateral closure is recommended, as hernias can occur on the right and left.

Synonyms!!navigator!!

None

Abbreviations!!navigator!!

Suggested Reading ⬆ ⬇

Gracia-Calvo LA, Ortega C, Ezquerra J. Laparoscopic closure of the inguinal rings in horses: literature review. J Equine Vet Sci 2014;34(10):1149–1155.

Kummer M, Stick JA. Abdominal hernias. In: Auer JA, Stick JA, eds. Equine Surgery, 4e. St. Louis, MO: WB Saunders, 2012:506–514.

Author(s) ⬆

Author: Alison K. Gardner

Consulting Editor: Margaret C. Mudge

Acknowledgment: The author and editor acknowledge the prior contribution of Laura Hirvinen.