8/3/2019 Ultrasonography for the Veterinary Nurse_Frank Busch

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VN TIMES0

DURING the past decade,

nurses in human medicine

have begun to incorporate

limited ultrasonography

(US) into obstetric nursing

practice.Guidelines have been estab-

lished or the perinatal nurses

that provide the recommended

content or the didactic and

clinical preparation needed.

Foetal US examination pro-

vides useul inormation on

the oetal status and comple-

ments the oetal heart assess-

ment just like in veterinary

medicine (Figure 1).

Unortunately, in veteri-

nary medicine no such estab-

lished role or the veterinary

nurse exists, although, in some

reerral centres, nurses have

become more involved in USprocedures. With the introduc-

tion o cheaper equipment, it is

hoped that in the not-too-dis-

tant uture, veterinary nurses

may play a major supportive

role in US, as they have done or

many years in radiography.

This article aims to give a

short introduction to US, the

objective being to involve vet-

erinary nurses in the diagnostic

procedure and to highlight how

use o this well-established

medium can be made more

rewarding.

Examination o the thorax

using US to study heart dis-

ease oten necessitates more

specialised equipment, and

thereore is not covered in

this article.

TErMInology

Ultrasound: High-requency

sound waves. Ultrasound

waves can be bounced o tis-

sues using special devices. The

echoes are then converted into

a picture called a sonogram.

Ultrasonography allows us to

get an inside view o sot tis-

sues and body cavities, without

using invasive techniques. It is

oten used to examine a oetusduring pregnancy. There is no

convincing evidence o any

danger rom this.

Transducer probe: The probe

is the main component o

the ultrasound machine. The

probe produces the sound

waves and receives the echoes.

Take good care o it its the

most expensive part o the

ultrasound machine.

Transducer probes come

in many shapes and sizes, as

shown in Figure 2. The shape

determines its ield o view,

and the requency o emitted

sound waves determines how

deep the sound waves pene-

trate and the resolution o the

image. In small animal prac-

tice, 5.0MHz and 7.5MHz trans-

ducers are used or the majority

o work.

In addition to probes that

can be moved across the sur-

ace o the body, some probes

are designed to be inserted

through body openings (vagina,

rectum, oesophagus) so that

they can get closer to the organ

being examined (uterus, pros-

tate gland, stomach); being

closer to the organ can give

more detail.In veterinary medicine we

deal primarily with the so-called

B-mode (two-dimensional and

real-time US). The strength o

the returning echo determines

the shades o black, grey or

white. The depth is assessed by

the time taken or the echo to

return to the transducer.

The echo strength is related

to the acoustic impedance o

tissue; ie, resistance to fow o

sound waves. Very little US is

refected by even small amounts

o fuid, hence the monitor will

show a black picture (described

as anechoic areas or echolu-cent areas).

Conversely, strong echoes,

such as those rom ibrous

tissue, will ultimately create a

white picture on the monitor

(described as hyperechoic or

echodense areas). The ultra-

sound beam is blocked by air

and bone.

In the UK, we are usually

taught to start rom the bladder

and continue the US journey

cranially towards the liver

and diaphragm.

nurSIng InpuT

If you are conducting the USexamination yourself or are

assisting your veterinary sur-

geon, there are a number of

preparatory steps to be taken.

The setting

Find a quiet room that can be

darkened. Always easier said

than done, but it is important

to undertake a complete ultra-

sound examination including

all the organs even i the

patient presented or a problem

relating to one organ only. A

rushed US exam is just not pos-

sible and signicant ndings

can be missed.

Equipment

Set the unit up saely, ideally

on a trolley, so the machine

can be rotated around the

patient. Switch the machine

on only ater you have attached

the probe to the unit and ater

you have made sure the probe

has been cleaned since its last

use. Never use spirit to clean

the probe; use a sot cloth ortissue instead.

The patient

Hopeully, your patient wont

be the spiteul tortoiseshell

cat that usually terrorises the

neighbourhood or the biting

Rotti rom hell.

But, i sedation is required,

so be it. You should aim to

clip the hair rom the entire

abdomen in most cases, but

certainly the caudal abdomen

when doing pregnancy exams.

Make the owner aware o the

extent o shaving necessary and

ensure you have consent rom

the owner with regard to seda-tion and/ or shaving.

Modus operandi

There is no right or wrong way

o holding the probe, as long

as you keep your wrist relaxed

and eel that you get good con-

nection between the probe and

the skin.

Use a silent mini-hoover to

remove the hair o the body

surace and lots o lubrication

o ultrasound-specic gel.

Placing the ultrasound

gel container in a jug o

warm water will avoid acooling eect on the patient

and will be more comortable

when you apply it to the skin.

Additionally, apply a good por-

tion o gel on to the probe.

The patient will need to be

restrained in lateral and/or

dorsal recumbency.

an IMagIng Tour

Start by trying to locate the

bladder and remember that

US is more dicult on a small

or empty bladder, and diuse

bladder thickening is more

dicult to see on the empty

bladder.Very little ultrasound is

refected by fuid, hence, you

should be able to ind the

bladder easily as it will show

up as a black area on your mon-

itor in the caudal abdomen

(Figure 3).

US imaging o the abdomen

is generally more sensitive

than radiology or evaluation

o the parenchymal organs

(you will soon learn to appre-

ciate the normal appearance o

the dierent organs) and

or the detection o ascites(Figure 4??).

In all animals with a radio-

graphic diagnosis o decreased

serosal detail or decreased

detail in the retroperitoneal

space, a US examination is

indicated to collect the fuid

or analysis and to rule out a

bleeding mass or a cause o the

ascites. Oten a mass is not vis-

ible on the radiographs but can

be seen on US. In some cases

US-guided aspirates can be

obtained and lead to a deni-

tive or presumptive diagnosis.

Ultrasound is a very sensi-

tive tool or assessing the elinekidney in cats with renal dis-

ease. Normal eline kidneys are

3cm to 4.5cm in length and

have a well-dened cortical and

medullary interace. The dis-

eased kidney will oten appear

hyperechoic and is very irreg-

ular. In cats with cystic disease

the kidney is very enlarged and

will have numerous cysts in the

renal cortex and the medulla

(Figure 4?).

Ultrasonography: a whistle-stop tour

Figure 1. Ultrasound can be used in the assessment

of the foetal heart in human and animal patients.

Figure 2. There are many types of transducer probe.

Figure 3. Bladder (left) and bladder and haemabdomen.

Figure 4. A feline kidney

with polycystic kidney disease

(above).

Figure 5 (A) Most hepatic

masses are are easily seen on

ultrasonography. (B) There is

usually a marked change in the

echogenicity and texture of

the cancerous mass compared

to the surrounding tissue.

FrankBusch, PhD, MRCVS

gives a guide to the techniques and equipment used

in ultrasonography in the veterinary practice

A

B

Practical

8/3/2019 Ultrasonography for the Veterinary Nurse_Frank Busch

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DECEMBER 2006 11

Small kidneys usually have

an irregular appearance on

both US and radiographic

studies. This irregular appear-

ance is due to brosis and scar-

ring o the damaged portion

o the kidney and secondary

capsular irregularity. On ultra-

sound examination the kid-

neys can appear hyperechoic

or striated.

Renal and lower urinary tractcalculi can be seen on radi-

ographic images, but some

calculi are not obvious. These

include urates and some o

the struvite calculi. The cal-

cium oxalate calculi are usually

very opaque and are easily seen

on survey studies.

The calculi seen in small ani-

mals are obvious on US exam-

ination. The calculi are very

echogenic and cause a large

amount o shadowing in the

distal eld.

Evaluation o the liver with

ultrasound is oten more

rewarding than with radio-graphic exams.

An abdominal ultrasound

is indicated or all animals in

which an enlarged liver or mass

is seen on radiography. There is

usually a remarkable change in

the echogenicity and texture o

the mass compared to the sur-

rounding liver tissue (Figures

5 and 6). Another benet is

that i a mass is present it can

be aspirated or biopsy samples

can be obtained.

In dogs and cats with unregu-

lated diabetes, the liver is oten

echogenic and enlarged. The

echogenicity changes are most

consistent with at deposition

in the liver.

Evaluation o the icteric

animal should include ultra-

sound as a baseline test to

rule out hepatic causes such

as obstruction o the biliary

tree, gall bladder disease andliver masses. One cause o

icterus and elevated bilirubin

is a mucocele (Figure 6). This

is a mass-like accumulation o

very thick bile and debris that

can cause the gall bladder to

rupture. As you may know, the

gall bladder is not routinely vis-

ualised on radiographs.

US examination o the

spleen is indicated in all ani-

mals with a palpably enlarged

spleen or one that appears

enlarged and irregular on

radiography. It is very easy to

discern rom the other abdom-

inal organs as it is normallyvery echogenic (Figure 7)

and very supercial. In the cat

it is usually conned to the right

side and is around 1-2cm in

width. The enlarged spleen in

the cat may extend across the

mid-abdomen and will usually

cover the let kidney.

In animals with torsion o

the spleen, the spleen is very

hypoechoic and there is a vari-

able amount o ascites present.

Splenic masses are oten com-

plex in texture and this may

represent haemorrhage in and

around the mass or may be

secondary to the cell type in

the mass.

Bear in mind that in animals

that are sedated or anaesthe-

tised the spleen can be moder-

ately enlarged. Even i enlarged,

the texture remains normal;

the spleen does not become

hypoechoic.US imaging o the small intes-

tine is very useul in dening

masses and interrogation o

the wall layers o the bowel.

The most prominent wall layer

o the bowel is the mucosal

layer and this is universally very

hypoechoic (Figure 8). On US

the normal width o the small

intestinal wall is up to 5mm

and, in the cat, it is closer

to 4mm. Bowel wall width

changes are oten accompa-

nied by an increase in the size

o one or more layers o the

small intestine.

The lymph nodes, pancreasand other small structures,

such as the adrenal glands,

cannot be seen using survey

abdominal radiographs or

even contrast studies. The

adrenal glands lie in close

proximity to each kidney.

Normal glands are bilobed

and are sometimes dicult to

nd on routine examinations.

In animals with adrenal hyper-

plasia the glands can become

easy to see as they are large

and, in some cases, irreg-

ular. Approximately 50 per

cent o adrenal tumours can

mineralise.

The pancreas lies caudal

to the stomach in the let

cranial abdomen and has a

similar texture to the mesen-

tery. On the right side o

the animal, the pancreas is

supericial and lies medial

to the duodenum over theright kidney.

In cases o pancreatitis

the pancreas becomes very

enlarged and is usually hypoe-

choic. This region o decreased

echogenicity is surrounded by

echogenic mesentery, which

is reactive. Most pancreatic

masses are o mixed echo-

genicity and can be well or

poorly dened.

And dont orget to think

outside the box whoever

came up with the idea to scan

the eye? Well, its a very useultool in diagnosing retrobulbar

abscesses (Figure 9) or oph-

thalmic neoplasias.

Figure 6. Gall bladder mucocele. Figure 7. Spleen with splenic nodule.

Figure 8. Small intestine. Figure 9. Retrobulbar abscess.

By improving standards o

training, increasing responsi-

bility and raising the bar or

VNs, it is hoped this will lead

to higher morale and increased

job satisaction. It isnt an unre-

alistic expectation that nurses

should become more involved

in diagnostic procedures and

that the veterinary team would

benet, and you could increase

your career options.Reerences can be obtained

rom the author on request

(masterkwerky@aol.com)

Practical