ABSTRACT: Ultrasonography as a technique offers the advantages of being widely available, non-invasive and can often be performed on the conscious patient. However, the environment in which the examination is performed, and patient preparation and co-operation, can have a significant outcome on the quality of the examination. Boisterous or aggressive patients, a noisy environment and blunt clippers can all contribute to a non-diagnostic examination or lead to lesions being missed. A routine, including sedation and general anaesthesia protocols, should be established for all ultrasound examinations. Unstable animals should be stabilised before ultrasound exanimation. For interventional procedures the patient should be immobilised, coagulation status determined and vital parameters monitored.

Ultrasonography has been employed in the diagnosis of abdominal and thoracic disease in small animals for almost 40 years. Once the preserve of referral institutions, it is now widely available in general practice. This article briefly reviews the principles of diagnostic ultrasound in small animals and focuses on the aspects and goals which are of particular significance to the VN in the clinical setting.

Patient preparation

Although an understanding of – and experience in – ultrasonography is essential for successfully interpreting and performing an ultrasonographic examination, patient preparation and restraint are as important. Ultrasonography is attractive to both the owner and the veterinarian because it is non-invasive in nature and it is potentially possible to perform a complete examination in the co-operative conscious patient.

Many examinations are, however, frustrated by boisterous, anxious, fractious or agitated patients. Efforts should be made to establish a routine for all ultrasound examinations and a smooth successful examination is usually one in which the welfare of the patient and comfort of the VN are addressed, allowing the clinician to scan without distraction.

The benefits of any ultrasonographic examination are usually directly related to the comfort and degree to which the patient co-operates. Studies should be performed in a quiet environment, away from busy thoroughfares within the practice, and in a room with adequate dimmed lighting.

Examinations are usually performed with the patient lying on its side (lateral recumbency) or back (ventrodorsal recumbency), although those with pleural effusion or respiratory difficulties should not be placed in the latter position. Cardiac examinations and some parts of the abdomen require scanning from beneath the patient positioned in lateral recumbency.

Practicalities of tables

Purpose-built ultrasound tables, with a hole cut into the tabletop, are ideal – but expensive. To overcome this, portable tables are available which can be placed on a tabletop or homemade boards with a cut-out on one side are used.

Whilst these devices are suitable for smaller and co-operative patients, the limitations and dangers of these constructions in large patients should be considered as significant stress can be placed on the VN’s spine as he or she is required to stretch across a wide board to restrain the patient.

An alternative is to use an ultrasound mattress with the cut-out close to the VN restraining the patient and with the additional benefit of a soft bed for reassurance.

In Figure la, the ultrasound mattress is designed to allow the animal to be held as close possible to the nurse. This – together with placing a sandbag along the spine of the patient – provides support, comfort and reassurance for the patient.

Figure 1a: The ultrasound mattress is designed to allow the animal to be held as close as possible to the nurse 

The cut-out can be adjusted or removed to allow the heart to be examined; or parts of the abdomen, such as the duodenum and pancreas, to be examined from beneath the patient. Compare this secure comfortable set-up with Figure 1b. Although the ultrasound table has a cut out to allow scanning from underneath, it is not secure for either patient or nurse.

Figure 1b: Although this ultrasound table has a cut-out to allow scanning from underneath, it is not secure for either patient or nurse

Figure 1c shows scanning of the dependent areas of the patient using a cut-out.

Figure 1c: Scanning of the dependent areas of the patient using a cut-out

Lifting and restraint

Lifting the patient on to the table is an important step, because many patients will panic and struggle, especially if they are ‘flicked’ directly into lateral recumbency. To avoid this situation, a stable hydraulic table is ideal. Alternatively lift the patient on to the table in a standing position first, then the clinician should fold the hindquarters down and towards him/herself, followed by the forelimbs, whilst the head is supported throughout. Too frequently the head is not supported and allowed to bang onto the tabletop which inevitably leads to an agitated patient.

Due consideration should be given to any orthopaedic condition when the animal is restrained, and soft bedding is obligatory. Most patients feel more secure with their back supported against the restraining VN or a large sandbag. The sandbag also serves to allow the wrist and forearm of the VN to be supported in a more natural unstressed position over the neck of the patient (Figure 2a).

Figure 2a: The sandbag behind the cat's neck supports the VN's arm and avoids excessive pressure on the neck, a more comfortable position for
both restrainer and patient

The lower limbs, in particular, should be supported because they are inevitably used by the patient to lever itself from the examination. Some patients have sensitive feet and holding the carpi/tarsi or the antebrachii is better tolerated.

Proper planning should allow a sufficient number of assistants to be available for restraint. Attempts to restrain boisterous or large dogs by a single person are ludicrous and, moreover, dangerous. This measure applies equally to fractious cats in which circumstance two restrainers allow the cat to be reassured by scratching or stroking of the head. This provision at least allows as complete an examination to be performed and reduces the risk of overlooking important findings.

In particular, in conscious, stable cats the risk of a bite to the hand restraining the neck can be avoided by using two restrainers, the supporting sandbag or temporary use of a flexible Buster collar or light muzzle. The possibility of a cat bite is not an acceptable risk and alternative steps to achieve adequate restraint should be taken. Some cats prefer to rest their heads above the restrainers wrist than to have a wrist placed across the neck (Figure 2b).

Figure 2b: Some cats are more settled with the head resting on the restrainer's arm

Many patients will accept light restraint once settled in position, but tend to be extremely sound-sensitive and will struggle when startled by sharp noise. This includes the scraping of chairs and doors and, most importantly, noisy clippers. Discourage other people from entering the room once the examination commences. Clippers should be sharp, clean and quiet.

Few conscious cats will tolerate clipping for longer than 20 to 30 seconds. The owner should be warned that clipping will be necessary and provided with some idea of the extent of this clipping. Areas for clipping usually include along the costal arch and beneath the sublumbar muscles on both the left and the right. As the clinician develops more experience, smaller windows may be clipped. Occasionally the coat – for example, in dogs with suspected endocrine disease, such as hyperadrenocorticism (Cushing’s disease) – is thinned and there is little need for clipping.

The heart is usually examined with the transducer beneath the patient, using a cutout, and an ECG connected to the ultrasound machine can be attached; though this is not feasible for every examination. The ultrasound machine ECG electrodes should be attached to the patient during examination of the heart (echocardiography). Atraumatic crocodile clips are available from ultrasound vendors (Figure 3).

Figure 3: These clips are atraumatic, without the serrations of conventional crocodile clips, and are well tolerated by almost alt patients

Consider sedation

Sedation greatly facilitates the examination (cardiac examinations are almost exclusively performed in the conscious patient). Whilst boisterous or aggressive patients would appear to be more obvious candidates for sedation, sedation should not be excluded in older animals as they may be nervous, agitated or senile and present an even greater challenge. Pain and discomfort may also affect the ability to perform a complete examination.

The clinician should consider the clinical status and temperament of the patient and adjust dosages appropriately. A one size fits all’ approach to sedation should be avoided.

Any examination in which the patient is considered unstable should be abandoned. Oxygen should be supplemented by a mask or flow-by method, if necessary.

One of the advantages of ultrasound is that where disease is detected, it may be possible to sample by ultrasound- guided fine-needle aspiration or to obtain larger samples by ‘trucut’ needle biopsy (Figures 4a & 4b). It is essential that the patient is immobilised for these procedures.

Figures 4a & 4b: Technique for obtaining samples under ultrasound guidance

In Figure 4a, cystocentesis is being performed. The dog, in this case a bitch, is immobilsed on its back and the needle is passed through the linea alba to minimise discomfort to the patient. The needle (arrow) is aligned with the positional marker (blue light) on the transducer.

Figure 4b shows the ultrasonographic image of the hypodermic needle within the bladder lumen (arrow). The needle casts a shadow of multiple parallel lines.

Sedation is adequate for many fine-needle aspirates, but general anaesthesia is necessary in almost all cases of biopsy. Informed consent should be obtained from the owner in all cases as significant complications including major haemorrhage, introducing infection and death may occur.

Determination of the coagulation (clotting) status may not be necessary for all fine needle aspirates where the patient is considered stable and a platelet count is available. For ‘trucut’ biopsies, a full clotting profile is advisable.

The most important factors for early identification of complications are to assess risk and vital parameters (heart rate, respiratory rate, capillary refill time) before the procedure and planned monitoring after the procedure. Intravenous lines should be maintained and most patients should be hospitalised for six to eight hours after the procedure.

For abdominal procedures, the girth should also be monitored. An increase in abdominal girth can indicate intra abdominal haemorrhage. These crucial steps should be established and enforced by the VN. 


Andrew Holloway BVSc CertSAM DVDI DipECVDI MRCVS

Andrew qualified from the University of Pretoria in 1992. He spent eight years in general practice before joining the University of Cambridge as a visiting resident in radiology; and in 2006, joined the Animat Health Trust as clinical radiologist. He holds the RCVS and European Diplomas in Veterinary Diagnostic Imaging.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.00154.x or Veterinary Nursing Journal Vol 27 pp 86-88


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• VOL 27 • March 2012 • Veterinary Nursing Journal