Paranasal sinus: drainage ostia - enlargement in Horses (Equis) | Vetlexicon
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Paranasal sinus: drainage ostia – enlargement

ISSN 2398-2977


  • The paranasal sinuses are large but drainage through the nasomaxillary opening into the middle nasal meatus is through a long, compressed slit and is generally poor.
  • The rostral maxillary sinus and ventral conchal sinus have a separate drainage route to the rest of the paranasal sinuses.
  • Part of the surgical treatment of paranasal sinus disease may include establishing increased drainage by enlargement or augmentation of the drainage ostia.



  • Permanently improves paranasal sinus drainage.
  • Allows for packing of sinuses with exit out nostril, preventing need to reopen flap to remove packaging.


  • Requires bone flap procedure Paranasal sinus: bone flap technique to gain adequate exposure to establish drainage.
  • Often associated with profuse hemorrhage.
  • Some cases will have a permanent low grade inflammation of sinuses following this procedure - may have a permanent low grade nasal discharge.

Technical problems

  • Distortion of the sinuses from masses Paranasal sinus: cyst: respiratory neoplasia Respiratory: neoplasia may obviate normal architecture and make fenestration of the rostral portion of the ventral conchal sinus difficult.
  • Fenestration of the ventral conchal sinus is uncomfortable and may result in patient non-compliance if performed standing.

Alternative techniques

  • Lavage of sinuses Paranasal sinus: lavage: in acute cases simple lavage may improve the drainage by liquifying the material in the sinus and forcing it out through the normal ostia - less effective in chronic cases where persistent production of material, often of a thickened nature.
  • Lavage + ostia enlargement usually undertaken at same time.
  • Feeding from ground/exercise: useful in acute cases of sinusitis but limited effect in chronic case.

Time required


  • Aseptic skin preparation: 10 min.
  • General anesthesia induction and maintenance: 20 min.


Decision taking

Criteria for choosing test

  • Drainage may be warranted in any case of paranasal sinus disease which is subjected to surgical treatment.

Risk assessment



Veterinarian expertise

  • Thorough knowledge of paranasal sinus and dental anatomy is critical for success.
  • Ability to assess hemorrhage and order a blood transfusion if needed.

Anesthetist expertise

  • Ability to competently anesthetize a horse under GA or sedate a horse if procedure done standing.
  • Ability to evaluate hypoperfusion resulting from blood loss including tachycardia, hypotension; ability to administer blood transfusion.

Nursing expertise

  • Assistance with a GA if required.
  • Ability to pass Chamber’s catheter up ipsilateral nostril.
  • Knowledge of oscillating saw set-up if this is to be used.

Other involvement

  • A competent horse handler is necessary if procedure is to be done standing.
  • Laser fenestration of the ventral conchal sinus is described using a transendoscopic diode laser.

Materials required

Minimum equipment

Ideal equipment

  • Same as bone flaps Paranasal sinus: bone flap technique, ie:
    • Oscillating bone saw or hammer and sharp osteotome.
    • Periosteal elevator(s).
    • Steinmann pins 2-3 mm.
    • Pin chuck.
  • Thin wire guide or Chamber's catheter to facilitate sinus packing exiting ipsilateral nasal passages.

Minimum consumables

  • Same as bone flaps Paranasal sinus: bone flap technique, ie:
    • 2-0 absorbable suture material, eg polyglactin 910 (Vicryl), polydioxanone.
    • 2-0 or 0 non-absorbable suture material, eg polypropylene.
  • Seton bandage or foley catheter.

Ideal consumables



Dietary preparation

  • Standard dietary modification.

Site preparation

  • Same as bone flaps Paranasal sinus: bone flap technique - both frontonasal and maxillary flap techniques can allow access to enlarge the drainage ostia.
  • Standard aseptic preparation (clean, shave, swab and drape).
Do not use chlorhexidine or alcohol near the cornea.

Other preparation

  • Cross-matching Blood: cross-matching the patient with suitable blood donors and, preferably before surgery, collect up to 8 l whole blood - store in citrate in a cool environment.




Step 1 - Bone flap

Core procedure

Step 1 - Ostia creation 

  • During frontonasal flap surgery it is common practice to break down the bulla of the ventral conchal sinus and the rostral edge of the frontomaxillary opening to allow access to the rostral maxillary sinus and ventral conchal sinus.
  • If the lateral and ventral walls of the dorsal conchal sinus and the underlying ventral concha are disrupted (greater access to rostral maxillary sinus and ventral conchal sinus) this will establish an opening from each conchal sinus into the nasal cavity which can be enlarged.
  • To disrupt the rostral portion of the ventral conchal sinus, therefore creating an ostia from sinus to nasal passage, have an assistant use a Chamber’s catheter threaded with large gauge suture to fenestrate the rostral portion of the ventral conchal sinus by traveling up the ipsilateral nostril.
  • Once the surgeon visualizes the Chamber’s catheter/suture, the suture may be tied to sterile packing prepared as below to pack the sinus.
Pre-measure the Chamber’s catheter against the horse’s head to gauge depth of placement; injury to the ethmoids by passing the Chamber’s catheter too caudally will result in frank hemorrhage.
  • In maxillary sinus flaps an opening can be made into the nasal passage through the ventral concha to allow drainage (can be difficult in young horses due to high dental alveoli).
  • An approach to the ventral conchal sinus from the rostral maxillary sinus can be performed in the bony portion underlying the infraorbital canal.
Damage to infraorbital nerve may cause permanent headshaking and must be avoided at all costs.
  • Enlarge openings using scissors or rongeurs.
Creation and enlargement of the ostia should be the last step before closure, as hemorrhage following fenestration is usually profuse.

Step 2 - Control hemorrhage

  • Control hemorrhage (usually profuse) by packing sinuses with gauze bandage soaked in 1% dilute povidone-iodine saline (or occasionally 1:10,000 epinephrine Epinephrine).
  • Fold bandage into sinus and draw free end: through ostia and out of the nasal passage and suture/tie to false nostril.


Step 1 - Maintain ostia patency

  • Maintain ostia patency by drawing a gauze bandage or foley catheter/tube out through the ostia, down through the nasal passage and attach to the false nostril and/or head collar.
    Thin wire guide or suture through the Chamber's catheter will make this easier.

Step 2 - Repair bone flap 


Immediate Aftercare


  • Monitor airflow through contralateral nostril.
  • Monitor packing sutured to false nostril.

Packing removal

  • Packing must be removed 24-48 h after surgery to mitigate risk of infection.
  • Sedation is often indicated, as pulling packing through the nostril is uncomfortable.
  • To pull packing, cut the suture attaching packing to false nostril and pull robustly in a downward direction.
  • Have a competent horse-handler hold the horse during the procedure.
The patient may respond to packing pulling by backing up quickly. Ensure a clear path behind the horse and that the horse handler is adequately warned.Hemorrhage may occur after pulling the packing. This usually self-resolves, but should be monitored, especially if hemorrhage was severe during surgery.

Fluid requirements

General Care

  • Upper respiratory tract (URT) obstruction may occur - a tracheotomy tube should be to hand or fitted as required Trachea: tracheotomy.


Antimicrobial therapy

  • Peri-operative and post-operative antibiotics, eg penicillin Penicillin G, gentamicin Gentamicin, (3-5 days minimum) depending upon primary disease process.

Other medication

  • Vigorous sinus lavage during post-operative period after packing removal will keep the new ostia patent Paranasal sinus: lavage.

Wound protection

  • A head bandage is recommended for 3-5 days after surgery or longer if patient is observed to be irritating surgical site.

Special precautions

  • URT obstruction - nasal passages - pass 20 gauge endotracheal tube up contralateral nostril - tracheotomy tube may be required Trachea: tracheotomy.
  • Excessive hemorrhage - blood transfusions Blood: transfusion may be required.

Potential complications

  • Excessive hemorrhage.

Long term Aftercare

Follow up

  • It is common to irrigate sinuses daily for up to 10-14 days post-operatively (particularly in septic and destructive lesions).
  • Mucopurulent fluid may drain from sinuses and down nasal passages initially but should cease in 10-14 days in normal cases.



Reasons for treatment failure

  • Too small a hole for the new ostia will eventually seal as the area heals → poor drainage.


  • Usually good with permanently effective increased drainage.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kološ F, Bodeček Š & Žert Z (2017) Trans-endoscopic diode laser fenestration of equine conchae via contralateral nostril approach. Vet Surg 46 (7), 915-924 PubMed.
  • Barakzai S Z & Dixon P M (2014) Standing equine sinus surgery. Vet Clin Equine Pract 30 (1), 45-62 PubMed.
  • Dixon P M & O'Leary J M (2012) A review of equine paranasal sinusitis: medical and surgical treatments. Equine Vet Ed 24 (3), 143-158 WileyOnline.
  • Dixon P M, Parkin T D, Collins N et al (2012) Equine paranasal sinus disease: a long-term study of 200 cases (1997–2009): ancillary diagnostic findings and involvement of the various sinus compartments. Equine Vet J 44 (3), 267-271 PubMed.

Other sources of information

  • Beard W (2014) Frontonasal and Maxillary Sinusotomy Performed Under General Anesthesia. In: Advances in Equine Upper Respiratory Surgery​. Ed: Hawkins J. Wiley. pp 177-183
  • Nickels F A (2012) Chapter 43 - Nasal Passages and Paranasal Sinuses. In: Equine Surgery. 4th edn. Eds: Auer J A & Stick J A. W B Saunders, USA. pp 557-568.
  • Tremaine W H & Freeman D E (2007) Disorders of the Paranasal Sinuses. In: Equine Respiratory Medicine and Surgery. Saunders Elsevier, USA. pp 403-404.