Research Paper| Volume 43, ISSUE 6, P652-661, November 2016

Sonographic evaluation of epidural and intrathecal injections in cats



      To describe the ultrasonographic anatomy of the caudal lumbar spine in cats and to detect ultrasound (US) signs associated with epidural or intrathecal injection.

      Study design

      Prospective, clinical study.


      Twenty‐six client‐owned cats.


      Transverse (position 1) and parasagittal (position 2) two‐dimensional US scanning was performed over the caudal lumbar spine in all cats. Midline distances between the identified structures were measured. Cats assigned to epidural injection (group E, n = 16) were administered a bupivacaine–morphine combination confirmed by electrical stimulation. Cats assigned to intrathecal injection (group I, n = 10) were administered a morphine–iohexol combination injected at the lumbosacral level and confirmed by lateral radiography. The total volume injected (0.3 mL kg−1) was divided into two equal aliquots that were injected without needle repositioning, with the US probe in positions 1 and 2, respectively. The presence or absence of a burst of color [color flow Doppler test (CFDT)], dural sac collapse and epidural space enlargement were registered during and after both injections.


      US scanning allowed measurement of the distances between the highly visible structures inside the spinal canal. CFDT was positive for all animals in group E. In group I, intrathecal injection was confirmed in only two animals, for which the CFDT was negative; seven cats inadvertently and simultaneously were administered an epidural injection and showed a positive CFDT during the second aliquot injection, and the remaining animal was administered epidural anesthesia and was excluded from the CFDT data analysis. Dural sac collapse and epidural space enlargement were present in all animals in which an epidural injection was confirmed.

      Conclusions and clinical relevance

      US examination allowed an anatomical description of the caudal lumbar spine and real‐time confirmation of epidural injection by observation of a positive CFDT, dural sac collapse and epidural space enlargement.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Veterinary Anaesthesia and Analgesia
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Brondani JT
        • Luna SP
        • Padovani CR
        Refinement and initial validation of a multidimensional composite scale for use in assessing acute postoperative pain in cats.
        Am J Vet Res. 2011; 72: 174-183
        • Casoni D
        • Rohrbach H
        • Spadavecchia C
        Total spinal anaesthesia following spinal lumbosacral injection of bupivacaine 0.5 per cent in a cat.
        Vet Rec Case Rep. 2014; 2: 1
        • Chin KJ
        • Karmakar MK
        • Peng P
        Ultrasonography of the adult thoracic and lumbar spine for central neuraxial blockade.
        Anesthesiology. 2011; 114: 1459-1485
        • Dudley NJ
        B-mode measurements.
        in: Hoskins PR Thrush A Martin K Whittingham TA Diagnostic Ultrasound – Physics and Equipment. Greenwich Medical Media Ltd, USA2003: 75-86
        • Dyce K
        • Sack W
        • Wensing C
        Textbook of Veterinary Anatomy. 4th edn. Saunders Elsevier, USA2010
        • Etienne AL
        • Peeters D
        • Busoni V
        Ultrasonographic percutaneous anatomy of the caudal lumbar region and ultrasound guided lumbar puncture in the dog.
        Vet Radiol Ultrasound. 2010; 51: 527-532
        • Fletcher TF
        • Malkmus SA
        Spinal anatomy of experimental animals.
        in: Yaksh TL Spinal Drug Delivery. Elsevier, USA1999: 71-96
        • Gregori T
        • Viscasillas J
        • Benigni L
        Ultrasonographic anatomy of the sacrococcygeal region and ultrasound-guided epidural injection at the sacrococcygeal space in dogs.
        Vet Rec. 2014; 175: 68-71
        • Hogan QH
        Epidural anatomy: new observations.
        Can J Anaesth. 1998; 45: R40-R48
        • Jones RS
        Epidural analgesia in the dog and cat.
        Vet J. 2001; 161: 123-131
        • Karmakar MK
        • Li X
        • Ho A
        • et al.
        Real-time ultrasound-guided paramedian epidural access: evaluation of a novel in-plane technique.
        Br J Anaesth. 2009; 102: 845-854
        • Liotta A
        • Busoni V
        • Carrozzo MV
        • et al.
        Feasibility of ultrasound-guided epidural access at the lumbo-sacral space in dogs.
        Vet Radiol Ultrasound. 2014; 56: 220-228
        • Lundblad M
        • Eksborg S
        • Lönnqvist PA
        Secondary spread of caudal block as assessed by ultrasonography.
        Br J Anaesth. 2012; 108: 675-681
        • Maierl J
        • Liebich HG
        Investigations on the postnatal development of the macroscopic proportions and the topographic anatomy of the feline spinal cord.
        Anat Histol Embryol. 1998; 27: 375-379
        • Otero PE
        • Campoy L
        Epidural and spinal anesthesia.
        in: Campoy L Read M Small Animal Regional Anesthesia and Analgesia. Wiley-Blackwell, USA2013: 227-260
        • Otero PE
        • Zaccagnini AS
        • Fuensalida SE
        • et al.
        Use of electrical nerve stimulation to monitor lumbosacral epidural needle placement in cats.
        Vet Anaesth Analg. 2014; 41: 325-329
        • Otero PE
        • Verdier N
        • Zaccagnini AS
        • et al.
        The use of a nerve stimulation test to confirm sacrococcygeal epidural needle placement in cats.
        Vet Anaesth Analg. 2015; 42: 115-118
        • Raghunathan K
        • Schwartz D
        • Connelly NR
        Determining the accuracy of caudal needle placement in children: a comparison of the swoosh test and ultrasonography.
        Paediatr Anaesth. 2008; 18: 606-612
        • Ramsey HJ
        Fat in the epidural space in young and adult cats.
        Am J Anat. 1959; 104: 345-379
        • Roberts SA
        • Guruswamy V
        • Galvez I
        Caudal injectate can be reliably imaged using portable ultrasound – a preliminary study.
        Paediatr Anaesth. 2005; 15: 948-952
        • Russell W
        Visual swoosh test.
        Paediatr Anaesth. 2008; 18: 1237-1238
        • Skarda RT
        • Tranquilli WJ
        Local and regional anaesthetic and analgesic techniques: cats.
        in: Tranquilli WJ Thurmon JC Grimm KA Lumb & Jones' Veterinary Anaesthesia and Analgesia. 4th edn. Blackwell Publishing, USA2007: 595-603
        • Thomas CE
        • Combs CM
        Spinal cord segments. A. Gross structure in the adult cat.
        Am J Anat. 1962; 110: 37-47
        • Triffterer L
        • Machata AM
        • Latzke D
        • et al.
        Ultrasound assessment of cranial spread during caudal blockade in children: effect of the speed of injection of local anaesthetics.
        Br J Anaesth. 2012; 108: 670-674
        • Tsui B
        • Leipoldt C
        • Desai S
        Color flow Doppler ultrasonography can distinguish caudal epidural injection from intrathecal injection.
        Anesth Analg. 2013; 116: 1376-1379
        • Valverde A
        Epidural analgesia and anesthesia in dogs and cats.
        Vet Clin North Am Small Anim Pract. 2008; 38: 1205-1230
        • Weber WJ
        • Berry CR
        Determining the location of contrast medium in the canine lumbar myelogram.
        Vet Radiol Ultrasound. 1994; 35: 430-432