Visualizing Hydronephrosis: A New Imaging Protocol for Acute Renal Colic (ARC)

The assignment content discusses the assessment of Acute Renal Colic (ARC) using Ultrasound (US) and Non-Contrast Computed Tomography (NCCT) KUB scans. US can identify stones of 5mm diameter and above, but has limitations such as low detection rate for small stones, inability to provide accurate anatomical location, and operator dependency. On the other hand, NCCT KUB is the accepted gold standard with high sensitivity and specificity, but has limitations such as high radiation dose, need for expert image interpretation, and increased radiologists' workload. The study aims to investigate if NCCT KUB can be the modality of choice for initial assessment of ARC patients, reducing waiting lists and providing clearer information for pre and post ESWL procedures.

Plain Computed Tomography of Kidneys, Ureters and Bladder as a
First Diagnostic Option for Renal Colic Patients in Sohar Hospital
Acute Renal Colic:
Acute renal colic (ARC) is one of the most common patients symptoms seen in the
accident and emergency (A&E) departments and urology clinics worldwide. Renal colic
is caused by a urinary stone that affects about 10% to 15% of the population in their
lifetime, 50% of these people are predicted to experience a recurrence of urinary stone
in the first 10 years after the first incidence (Ahmed et al., 2010; Smith, 2012; Moore et
al., 2013; Moore et al., 2014; Lukasiewicz et al., 2014).
According to Vijayaraghavan et.al. (2009), over 7 million patients were seen in the A&E
departments in the United States of America (USA) in 2008 which resulted in an
estimated cost of 2.1 Billion dollars. There are approximately 360000 annual visits of
ARC in Oman hospitals (Al-Marhoon et al., 2013). Generally, renal stone affects more
male than females with a ratio of 3:1. The clinical presentation is usually symptoms of
colicky flank pain that irradiates to the groin, and sometimes is associated with
hematuria or single sided abdominal pain (Taourel et al., 2008; Sayani et al., 2011;
Nadeem et al., 2012; Leveridge et al., 2015). Generally, there are several methods of
diagnosing ARC which includes good patient`s history, clinical examination, laboratory
investigation and radiological investigation
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The Role of Imaging in the Assessment of ARC:
Various imaging techniques can be used to diagnose renal stones. These include
radiography of the kidneys, ureters and bladder (KUB), intravenous urography (IVU),
ultrasound (US) and computed tomography of the KUB (CT-KUB).
Plain KUB radiography:
In the last century plain radiography of the KUB was the initial radiological assessment
of ARC. This technique was not so accurate in detecting renal stones due to missing
50% of stones smaller than 5mm in size and their location in the lower portion of the
urinary tract system. Also, the stones may be obstructed by faecal matter and gases in
the bowel. It has been reported that the sensitivity and specificity of this technique in
detecting urinary stone was 18.3% and 77% respectively. However, the radiation
burden is very low (0.7mSv) in comparison to IVU (1.5 mSv) and CT (4.7 – 6.5 mSv)
which obviously is a benefit as it can be used for follow-up cases (Chuwdhury et al.,
2007; Kenniish et al., 2008; Peddu & Desai, 2009; Song et al., 2010).
Intravenous urography:
Intravenous urography involves the injection of a contrast agent into the anterior cubital
vein of the arm to opacify the kidneys and ureters in relation to the surrounding soft
tissue structures within the abdomen because the contrast has high atanomic number
which make it easily visualized in the x-ray image (Wang et al., 2008; Quirke et al.,
2011). Although IVU’s sensitivity and specificity of 59.1% and 94% is higher than for
plain KUB radiography, the technique has the following drawbacks; it provides limited
information about intra-abdominal pathology, very long examination time, risk of patient
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reaction to contrast agent such as collapse, itching and vomiting, and special
considerations are needed for diabetic patients and those with kidney disease as the
contrast agent needs to be excreted from the body to avoid any complications (Kenniish
et al., 2008; Lauritsen et al. in 2008; Mccombie et al., 2011).
Ultrasound imaging:
Ultrasound is basically a device which uses a high frequency sound waves to produce
images of the internal structures of the body without the use of ionization radiation
(Nicolau et al., 2015). Ultrasound is capable to visualises hydronephrosis which is an
indication of obstruction caused by stone, in addition it can identify large urinary stones
of 5mm diameter and above. The advantages of US include its portability which means
that it can be used at patients’ bed side, wide available, not invasive and it is cheap
compared with CT. Its major advantage is the lack of ionizing radiation and its
associated hazards (Patatas et al., 2012; Nicolau et al., 2015). On the other hand, US
limitations include low detection rate for small stones less than 5mm in size, and
inability to provide accurate anatomical location which can lead to misdiagnosis. Its
reported sensitivity is 45% and specificity of 88% (Pal and Mellon, 2008; Masselli et al.,
2015). It is also operator dependent since the accuracy can be differ from one operator
to another in terms of knowledge, experience and skills (Chen et al., 2015). However,
US remains the first line of assessing ARC when there is lack of CT equipment or
radiologists to interpret the images produced, and also for pregnant women and children
to avoid ionizing radiation risk. It is also recommended when either IVU or MRI is
contraindicated (Sayani et al., 2011; Curhan, 2014; Leveridge et al., 2015).
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Non-Contrast CT Assessment of ARC:
Non-contrast CT KUB has become the reference technique for suspected renal colic to
diagnose, plan treatment and explore differential diagnosis. Non-contrast CT KUB is the
accepted gold standard for investigating suspected renal colic cases due to its high
sensitivity and specificity of 98.9 %, and100 % respectively, in relation to other imaging
modalities (Patatas et al., 2012). In addition, non-contrast CT is a contrast- free
procedure, quick, safe and of reasonable cost (Chowdhury et al., 2007; Kennish et al.,
2008; Song, 2009).
Non-Contrast CT KUB is accurate in detecting both renal stones and extra-renal
abnormalities which is difficult to be diagnosed by the traditional radiological pathway of
a suspected renal colic such as: plain KUB radiograph, US and IVU. It is able to
accurately demonstrate stone size, shape and location. it can also demonstrate swollen
kidneys, perinephric edema, hydro nephrosis, periureteral edema and hydrouereter
(Taourel et al., 2008; Smith, 2012; Leveridge et al., 2015). However, non-contrast CT
limitations include its high radiation dose (4.7- 6.5 mSv), needs more expert for image
interpretation and it increases radiologists workload (Kenniish et al., 2008; Wang et al.,
2008).
Study rationale:
Sohar Hospital in Oman has 450 beds serving a population of over half a million people.
There is only one CT machine and two ultrasound machines which are used for eight
hours every day of the week. The current management pathway for ARC patients
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presenting to A&E is to treat the patient with pain killer and IV fluid, followed by plain
radiography of the KUB and then referral to the urologist according to the hospital
protocol for ARC patients’ management pathway. Due to workload pressure, either the
urologist or radiologist may not be available in the hospital to manage ARC patients
referred from A&E which results in some patients being admitted for treatment including
radiological assessment.
According to the statistics from the radiology department at Sohar Hospital; there were
1420 CT KUB examinations performed in the period between September 2013 and
September 2016. All these patients definitely have had some radiological examination
as initial investigation (EVIDENCE required – numbers per year) before the CT KUB scan such
as: US, IVU or plain KUB X-ray. This increases delay in radiological examinations,
patient radiation dose, risk of reaction to contrast media and use of limited radiological
resources. As a consequence, the financial cost is also increased due to multiple visits
and hospital admissions. Currently, the radiology department has no protocol for
imaging ARC patients which makes patients’ management and treatment pathway more
complicated, waste of resources and time which eventually can worsen the patients’
condition and increase the financial cost for the hospital.
YOU NEED TO INDICATE WHY THERE IS A LONG WAITING LIST IN CT IMAGING
1420 PATIENTS OVER 3 YEARS IS RATHER SMALL
This study aims to investigate if NCCT KUB can be the modality of choice for the initial
assessment of ARC patients by recommending it as the new imaging protocol instead of
the longer pathway currently being used. It is anticipated that its use will reduce the
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ARC patients imaging waiting list as well as providing clearer information for pre and
post ESWL procedures.
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