Crop Impaction

Introduction

The crop (ingluvies) is a diverticulum of the oesophagus located at the level of the tracheal bifurcation and slightly to the right.  The crop shape differs depending on the bird species; chickens and turkeys have a true crop (well developed, defined shape), ducks and geese have a rudimentary crop (long, narrow and occupies a small space) The crop structure is similar to the oesophagus, but it doesn’t produce mucous and has a high resident population of bacteria (lactobacilli species dominate).1,2

The crop is distensible to allow birds to swallow food whole, it provides a barrier to pathogens and plays a role in digestion (feed storage and moistening ingested food).2 The crop is emptied (by muscular movements) into the proventriculus, then ventriculus (gizzard) –  the rate of crop emptying is determined by gastrointestinal motility further along the tract, but generally the crop empties every 2 to 4 hours. The general health of the gastrointestinal tract may impact crop function.1,2

The crop is usually empty in the morning,  as birds eat through the day the food should be palpable within the crop. The crop is likely to be full in the evening to allow digestion of crop contents overnight.  Crop impaction can result from a failure of the crop to empty due to a foreign body or a gastrointestinal dysmotility issueFollowing crop impaction, there’s an increased risk of developing a pendulous crop.

Clinical Signs

References.2,3

Impacted crop predisposes birds to secondary sour crop. Rotting food retained in the crop disrupts normal commensal bacteria within the crop.

  • Firm mass palpated in the crop. 
  • Reduced faecal output or no faeces produced. 
  • Anorexia. 
  • Poor body condition (chronic cases).
  • Dehydration.
  • Halitosis.
  • Repeated neck extension (attempting to shift contents).
  • Not in lay.
  • Depression.
  • Death.

Diagnosis

References.3,4

  • History. 
  • Clinical signs. 
  • Physical exam.
  • Radiographs are useful in assessing the location of an obstruction and visualising the gastrointestinal tract. A barium study can also be done to assess transit time. 
  • PCV, total protein and uric acid are useful in assessing renal function and hydration prior to surgery.
  • Cytology of swabs from the crop can help identify secondary sour crop ie, overgrowth of bacteria / yeast / both. 
  • If crop impaction has previously been treated, then investigation for causes of gastrointestinal dysmotility may be warranted. 
  • Post-mortem findings. 

Treatment

Supportive

  • Cooking oil (e.g. olive oil) can be crop tubed and gently massaged into the mass to break it up and encourage the contents to pass naturally. This can be repeated every couple of hours. If the bird is hydrated, passing faeces, bright, alert and responsive, then leave the bird overnight to see if the mass reduces.
  • Never invert a bird to empty the crop, the risk of aspirating the fluid is extremely high.
  • If the bird is dehydrated, failing to pass faeces and generally in poor condition, then surgery would be recommended.3

Medical

  • Correct the fluid deficit. 
  • Antibiotic/antifungal therapy if indicated for sour crop. 

Surgical

  • Surgical removal of the crop contents (Ingluviotomy) may be required if the crop contents do not pass.2

Post Surgical Care

  • Provide appropriate analgesia.
  • Provide probiotics (to support the crop and gut treat dysbacteriosis).
  • Placement of a crop bra can help support the crop and help crop emptying, especially in cases where the crop was greatly stretched and distended prior to surgery. 
  • Small, regular soft meals to prevent gorging and stress on the surgical site. In severe cases, a liquid diet may be recommended for several weeks.3

Prognosis

Good, if no other underlying cause is present. If crop impaction/stasis is secondary to lower GI or reproductive disease, long term prognosis is poor. 

Transmission

No known risk of transmission between affected birds.

Zoonotic Risks

No known zoonotic risks.

Prevention

  • Avoid access to long grass to prevent gorging (predominant cause3).
  • Provide the birds with a balanced diet.
  • Provide grit (soluble and insoluble) to aid digestion.

Risk Factors

  • Stress.
  • Overcrowding.
  • Boredom.
  • Nutritional deficiencies.
  • Lack of available grit.
  • Ingestion of foreign material e.g. long grass, bedding, feathers, objects found around the garden such as plastic, string etc.
  • Sour crop may develop due to crop dysmotility.
  • Recurrence of crop impaction due to an undiagnosed gastrointestinal dysmotility issue e.g. Marek’s disease, neoplasia, parasites, lead toxicity. 3

References

  1. Classen, H.L. et al., 2016. The role of the crop in poultry production. World’s Poultry Science Journal . Vol:72 (3) p: 459 – 472. 
  2. Kierończyk, B. et al., 2016. Avian Crop Function – A Review. Annals of Animal Science 16(3):653-678.
  3. Greenacre and Morishita, 2015. Backyard Poultry Medicine and Surgery. A guide for Veterinary Practitioners. Page 230. 1st ed. John Wiley and Sons, INC. Oxford.
  4. Journal of Veterinary Diagnostic Investigation 2019, Volume: 31 issue: 3, pages: 368-370 [online] Available at: <https://journals.sagepub.com/doi/full/10.1177/1040638719843966> [Accessed 27/06/21].

Crop Impaction

Crop Impaction - View prior to surgery, Speedy - Credit Rebecca Gounaris
View prior to surgery, Speedy - Credit Rebecca Gounaris
Crop Impaction - Prior to surgery, Speedy - Credit Rebecca Gounaris
Prior to surgery, Speedy - Credit Rebecca Gounaris
Crop Impaction - Prep for Ingluviotomy, Speedy - Credit Rebecca Gounaris
Prep for Ingluviotomy, Speedy - Credit Rebecca Gounaris
Crop Impaction - Suture site post Ingluviotomy, Speedy - Credit Rebecca Gounaris
Suture site post Ingluviotomy, Speedy - Credit Rebecca Gounaris
Crop Impaction - Dilated crop, Eclair - Credit Rebecca Gounaris
Dilated crop, Eclair - Credit Rebecca Gounaris
Crop impaction - Turkey - Credit Rebecca Gounaris
Turkey - Credit Rebecca Gounaris